I've heard the phrase "dry run" being used with the meaning of rehearsal, experiment or test exercise in various contexts. For example:

  • They did a dry run of the demonstration before showing it to the CEO.

  • Practice with a dry run. Organise a dress rehearsal within two weeks of the wedding to ensure...

  • A dry run of the software release will be executed to ensure that the release plan is correct and clear to everybody.

However, wet run would not make sense in any of these contexts. So, why "dry"? Where does "dry run" come from?

  • 8
    I had always assumed, utterly without evidence, that it came from "dry assembly", the way a carpenter will put all the pieces of a work together first without glue ("dry") to test their fit. Commented Feb 27, 2011 at 1:36
  • @Malvolio I'd always assumed similar, that a "dry run" was testing out the machinery or application of a process without consuming any resources, hence a "dry" run as opposed to a production run. Commented Mar 10, 2011 at 20:52
  • 2
    My assumption was that it came from the prohibition when moonshine runners would run the route without carrying any alcohol to get to know the route better, and improve their speed for the actual run (hence a "dry" run). But my assumption probably comes from seeing one too many movies like Fast & Furious. lol Commented May 24, 2013 at 2:11
  • @Malvolio, Who told you that? How would you think of that?
    – Pacerier
    Commented Oct 16, 2015 at 9:28
  • "You see something, you hear a word, I thought that's what it was." No real basis. People said "dry assembly" or "dry fit"; other people said "dry run". I put them together. Commented Oct 16, 2015 at 12:07

6 Answers 6


According to World Wide Words, it originates from firemen doing speed competitions without carrying water.

The term run, more fully fire run, has for at least the past century been used by local fire departments in the USA for a call-out to the site of a fire. It was once common for fire departments or volunteer hose companies to give exhibitions of their prowess at carnivals or similar events. [...] These competitions had fairly standard rules, of which several examples appear in the press of this period, such as in the Olean Democrat of 2 August 1888: “Not less than fifteen or more than seventeen men to each company. Dry run, standing start, each team to be allowed one trial; cart to carry 350 feet of hose in 50 foot lengths ...”.

These reports show that a dry run in the jargon of the fire service at this period was one that didn’t involve the use of water, as opposed to a wet run that did. In some competitions there was a specific class for the latter, one of which was reported in the Salem Daily News for 6 July 1896: “The wet run was made by the Fulton hook and ladder company and the Deluge hose company. The run was made east in Main street to Fawcett’s store where the ladders were raised to the top of the building. The hose company attached [its] hose to a fire plug and ascending the ladder gave a fine exhibition.”

It’s clear that the idea of a dry run being a rehearsal would very readily follow from the jargon usage, though it first appears in print only much later.

  • The article linked to no sources. So we're supposed to just take their word for it, even if it's a made-up story?
    – Pacerier
    Commented Oct 16, 2015 at 9:28
  • @Pacerier: Not counting the 1888 Olean Democrat or the 1896 Salem Daily News?
    – mmyers
    Commented Oct 16, 2015 at 15:03
  • 1
    I don't see a link to "Olean Democrat of 2 August 1888" nor "Salem Daily News for 6 July 1896". I could say "Olean Democrat of 2 August 1888" wrote X, Y, Z, too, where X, Y, Z can be anything. So we're supposed to just take their word for it?
    – Pacerier
    Commented Oct 19, 2015 at 12:38
  • Perhaps someone with an account on stevenspointjournal.newspapers.com could do a search: stevenspointjournal.newspapers.com/search/#query=%22dry+run%22
    – Sam Hasler
    Commented Mar 15, 2016 at 11:43
  • 1
    See the New York Sun of August 24, 1888 for an account of "hose races": "They were governed by New York State rules, a dry run, one trial, standing start, not less than fifteen or more than seventeen men, cart to to carry 350 feet regulation hose, distance 200 yards to hydrant, attach and lay one line of hose 300 feet from hydrant, uncouple the sixth fifty-foot section from the seventh, put on pipe three full threads: ..."
    – Sven Yargs
    Commented Jan 4, 2019 at 7:00

In addition to the dried out riverbed, a dry run can also be a dry enclosure for poultry to run in. But for practice meaning, Etymonline.com says "Dry run is from 1940s" and there's plenty of US military examples of a practice without ammunition during WWII.

Military: firing practice without ammunition

American Speech defined the term during WWII. "Glossary of Army Slang", Vol. 16, No. 3, Oct., 1941:

DRY RUN. To practice; a dress rehearsal.

And "Remarks on 'Glossary of Army Slang'", Vol. 17, No. 1, Feb., 1942:

'DRY RUN (to practice; a dress rehearsal).' I never heard it used as a verb, or to mean a dress rehearsal. Originally a semi-official term for practice firing without ammunition, it is slang in other senses, such as a mail-call at which one receives no mail.

From a 1932 Coast Artillery Journal:

Later we had a short practice with the Navy; a so-called "dry run," which proved not so dry.

From a 1932 The Military Engineer description of 1918:

The French had designed a trestle for a bridge over the river and one over the canal and delivered them to us in trucks ready framed for erecting. Many dry-run erections were made on dark nights until the structures could be erected in ...

Also some army test flights, including this non-military 1934 test flight in Multiple lens aerial cameras in mapping:

Climb to altitude and if the area is near at hand study ground and map flight lines, while climbing. 5. Reaching altitude, make a trial or "dry" run. This enables the pilot to find his drift and the photographer to find the time between ...

(There are later test flights in in 1938's The principles and practice of surveying and 1941's Photogrammetric engineering and remote sensing.)

Unsubstantiated theories

Here's a theory with not much to back it up. The banks of dried riverbeds, dry runs, were useful as tactical cover for infantry. This 1914 Infantry Journal says:

In framing problems, take as few liberties with the landscape as possible. It borders on the ridiculous to state in a maneuver problem that a dry run is an unfordable river or that a hill is a marsh.

It's a stretch, but were dry river beds often used for infantry practice maneuvers? Did this lead to dry run becoming a practice without ammunition?

Another theory goes:

As per the etymology for "dry run", I wonder if the roots to its artillery past aren't stronger than what is given on the site... When muzzle-loading cannon is fired, the bore is swabbed out with a wet sponge on a pole so that the embers from the shot that was fired, do not prematurely ignite the gunpowder that is being loaded for the next shot. Of course, if the exercise is just a drill, there would be no need for a wet sponge. A dry one would be used. Hence, "dry run"?

I should add that when a firing range on a military base is ready to start shooting, the Range Commander asks for permission to "go wet". A flag is raised and the shooting starts.

I can't find any evidence for this, but there's definitely a strong military connection.

Firemen's races: practice run without water

However, the fireman theory is also good. The military use is practice firing without ammunition. The firemen's use is a practice run without water.

During firemen's races, each part of putting out a fire became its own event: a dry run: "running out the hose" over a distance and connecting to a hydrant; a wet test: "throwing out water" with given pressure over a distance; a coupling contest: attaching hose to the hydrant; a ladder climbing contest.

The 1894 The New York clipper annual ... containing theatrical, musical and sporting chronologies ... includes three instances of dry run in firemen's races, for example:

dry run, 200yds. to hydrant, attaching, unreeling 350ft. of regulation hose, breaking coupling and putting on pipe, each three full turns, cast 515lb, stripped, pipe 24[?] long, 51/2lb, carried by pipeman, who started with team.

So they run with the hose and attach to a hydrant, but in each, no mention is made of turning on the water. The same publication details other races describing a certain steam pressure and water pressure.

A 1910 The Harvester World details a similar Fire Department Contest, with a similar Dry Run event, with other events: Ladder Climbing Contest, Coupling Contest, and a Wet Test involving "throwing water".

The 1916 Tacoma: its history and its builders; a half century of activity

Eagle Hose Company of Old Tacoma won the "wet test" in 38 1/2. seconds. The "wet test" consisted of running 660 feet, connecting with a hydrant and throwing water. The "dry test" was won by a Vancouver, BC, company in 4 1/2 seconds. A squabble arose in the firemen's contests over the right of Struve, one of the Seattle firemen to participate, it being charged that he was a professional runner, which in fact he was. Some two years before he had run a race in Tacoma with Halstead, and had carried a 50-pound sack of flour on his shoulders as a handicap.

The British Fire Prevention Committee's 1907 Red Books tabulates the results of dry and wet tests. It also talks of a "for position of hydrants and run of hose, see Fig. 7." and several uses of "the hose was run out in [a direct line/the same direction]". So run appears to be the technical term for laying out hose, and perhaps why the US races are generally either "dry run" or "wet test" (in addition ladder climb or coupling contest) - each part of the drill is separated out.

  • 2
    In my experience in the military, firing a weapon without ammunition is a "Dry Fire."
    – Arluin
    Commented Jun 6, 2014 at 16:01
  • @Arluin, That begs the question: What's the origin of that? Why is a bullet wet?
    – Pacerier
    Commented Oct 16, 2015 at 9:29
  • 2
    @Pacerier Likely from these firemen's races. Dry run => practice run => no ammo. Wet run => real test with water => with ammo.
    – Hugo
    Commented Oct 16, 2015 at 10:51

I'm sceptical of World Wide Words claim that dry run originated from firemen practising, if only because it's such a limited context that I can't see how it would pass into general parlance.

On the other hand, bricklayers are everywhere, and have been for a long time. They often lay out a dry run of bricks without mortar for various reasons - chief among them being to make sure the interlocking brickwork "bond" will work out.

  • Bricks and mortar go way back so it's plausible, but strangely the earliest such dry run I found was in 1954 where it's used in quotes.
    – Hugo
    Commented Nov 24, 2011 at 21:22
  • 2
    @Hugo: I found an example from 1931, where it is explained as "army lingo". I think it more likely the army got it from firemen than from bricklayers. Commented Nov 24, 2011 at 21:55
  • Yes I saw that one myself earlier. I took it to mean the author didn't consider the expression to be in common parlance, but that needn't imply he knew he was transplanting an idiom from firefighters' drill sessions into a new context. Anyway, this NGram for just a dry run suggests it had no meaningful currency until after WW2, when there was a lot of rebuilding (in Britain, at least). Sometimes it's not the actual first use that matters, but when/why it became commonplace. Commented Nov 24, 2011 at 21:56
  • @Peter: Ah. Bit of confusion there. I was replying to Hugo. Yeah, I agree the army should be more in tune with firemen than bricklayers. But in terms of actual meaning, I still think "dry run" often implies "easily and safely repeated, with no permanent effects or high costs". Which seems central to a dry run of bricks, but only peripheral to firefighting drills. Commented Nov 24, 2011 at 22:12

From The Spectator (insurance magazine, New York and Chicago), 1931 or 1932:

In army lingo this is a "dry run" — a trial without ammunition.

So the term might have originated with firemen's drills, but come into widespread use after passing through the army first.

This was the first instance of "dry run" I found with the desired meaning in Google books, although there are numerous earlier instances of "dry run" meaning a watercourse that is dry most of the year, so it certainly appears that it came into widespread use by way of the army.

  • @FumbleFingers: The Spectator by Chilton Co. was a US property insurance review. Check the right hand column: "PEORIA ILLINOIS".
    – Hugo
    Commented Nov 24, 2011 at 22:51
  • oic. I'll delete my comment then. The British one is so profoundly "British" that possibility didn't really occur to me. Commented Nov 24, 2011 at 22:51
  • This. Which also explains the big jump in usage c. WWII. From Collins Dict.: 1. (Military) Military practice in weapon firing, a drill, or a manoeuvre without using live ammunition
    – Robusto
    Commented Sep 18, 2012 at 18:32
  • This comports with the phrase "dry fire", meaning to pull the trigger on a cocked gun without any ammo in the chamber. HOWEVER, most of the proposed explanations fail to explain why "dry" should mean "empty" (and "wet" mean "full"????). Points in favor of the firehose explanation.
    – Rob Lewis
    Commented Feb 4, 2020 at 17:12

"Dry training" in sport, such as non-running exercises for runners, probably comes from swimming.


Here's something I havn't seen here (or yet investigated). My wife postulated that "dry run" originated with printing: a dry run was a run without ink to make sure all the letters were properly aligned.

  • 5
    How would you know all the letters were aligned if you don't see the result of the print? This doesn't make sense. Commented Jun 4, 2012 at 18:56
  • 2
    Matt is right on the money. What printers actually do is have a wet run, and then check the registration marks or color bars for proper alignment. (You've probably seen those many times, when you tore apart a pack of milk, or other commercial packaging.)
    – RegDwigнt
    Commented Jun 4, 2012 at 19:14

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