"plumb" as far as I know is a predominantly American usage, as in "That was just plumb crazy!"

I thought plumb meant some kind of weight in bricklaying or such like, so how did it come to mean "absolutely"? What was its origin and history?

Edit: After Callithumpian's answer, I have a little addition:

Why is it a US usage chiefly, and why do not the British use it as much?

  • In my experience, Brits do in fact use plumb to mean "spot-on". Eg, "that's plumb-perfect". A company comes to mind that is called "plumb-something" (meaning perfect whatever-they-sell). HOWEVER perhaps the expression "plumb crazy" is NOT used in UK (I'm not sure), and THAT is why you say "less used in the UK". ie "plumb crazy" is (perhaps) not used in the UK, but "plumb" meaning spot-on, is indeed used. BTW a funny one in the UK (particularly amongst builders) is "tits", again meaning "spot on." (So, you finish installing a window .. you exclaim, "Tits." (!))
    – Fattie
    Commented Jun 15, 2011 at 15:54

9 Answers 9


Etymonline indicates that the "completely" sense of the word was an extension of the "exact measurement" sense of the word and dates this shift back to the mid-18th:

plumb (n.) c.1300, "lead hung on a string to show the vertical line," from O.Fr. *plombe, plomme "sounding lead," from L.L. *plumba, originally pl. of L. plumbum "lead," the metal, of unknown origin, related to Gk. molybdos "lead" (dial. bolimos), probably from an extinct Mediterranean language, perhaps Iberian. The verb is first recorded late 14c., with sense "to immerse;" meaning "take soundings with a plumb" is first recorded 1560s; figurative sense of "to get to the bottom of" is from 1590s. Plumb-bob is from 1835. Adj. sense of "perpendicular, vertical" is from mid-15c.; the notion of "exact measurement" led to extended sense of "completely, downright" (1748), sometimes spelled plump or plunk.

Edit re: British vs. American use:

I found this newsletter on British plumb bobs and noticed that another word used for the tool in several publications was plummet rather than plumb-bob. Perhaps plummet was a common enough name for the tool in England that it prevented the development of the extended sense of plumb as occurred in the U.S. This is only a guess.

Edit re: confusion with plum:

After seeing the OED references in @Simon's answer, I agree with @Peter's comment that there seems to be some confusion between the etymology of plumb and plum as intensifiers. I found this on plum at Etymonline:

plum O.E. plume, early Gmc. borrowing (cf. M.Du. prume, O.H.G. phruma, Ger. Pflaume) from V.L. *pruna, from L. prunum "plum," from Gk. prounon, later form of proumnon, from an Asiatic language. Change of pr- to pl- is unique to Gmc. Meaning "something desirable" is first recorded 1780, probably in ref. to the sugar-rich bits of a plum pudding, etc.

Some of the OED references seem to be examples of plum being used to mean "something desirable" rather than misspellings of plumb meaning "completely."

  • Why don't the British use it as much as the Americans? In fact, as far as I know, they don't seem to use it at all! Is there a reason why?
    – Thursagen
    Commented Jun 15, 2011 at 11:39
  • @Ham: See my edit as to a guess. Commented Jun 15, 2011 at 11:52
  • 1
    @Callithumpian, a pretty good guess...
    – Thursagen
    Commented Jun 15, 2011 at 11:56
  • "Plumb crazy" is used in en-gb, although to my surprise BNC only has one instance. Commented Jun 15, 2011 at 12:32
  • I thought a plummet was a lead stylus, i.e. a writing tool?
    – Marthaª
    Commented Jun 15, 2011 at 13:58

Lots of background and examples in other answers, but I really don't see anything at all unusual in this type of 'specialised meaning'.

Plumb weights are made of lead (Pb=plumbum), and they give straight vertical lines. That explanation is straight up (absolutely true), and it's straight to the point (absolutely focussed).

Does anyone ever wonder why we use straight in such figurative senses? I can't see why the American use of plumb is much different.

Brits don't say it simply because it calls to mind American 'hicks from the sticks' who are invariably plumb loco.


Callithumpian's answer is all you would need; except for an actual answer to 'how did it come to mean...?' Surely 'plumb vertical' is a builder's term, meaning 'precisely vertical as measured by plumbline', and it was taken up by outsiders who assumed it just meant very (I have seen it as plum as well as the variations in the dictionary).

  • I would have guessed plumb straight rather than plumb vertical, but I can't find either of these expressions in Google books before 1862 (when we get plumb straight meaning exactly vertical), long after plumb was being used as an intensifier. Commented Jun 15, 2011 at 14:09
  • @Peter Shor: My pa is a builder, and he just says a wall is plumb when it's vertical. I think anyone who says it's plumb vertical either likes tautology or likes American slang (and doesn't know the standard meaning of the word). Commented Jun 16, 2011 at 2:28
  • @Peter: "Plumb vertical" makes sense to me: A line can't be literally "plumb horizontal". A plumb line can only measure vertical lines. Well, I suppose in some cases you could stand the thing on end, use a plumb line to make sure it's straight, and then lie it down.
    – Jay
    Commented Jan 19, 2012 at 15:49

I find the 'plumb' arguments abstruse, myself.

If things can be 'peachy keen' why can't they be 'plum crazy'?

  • Certainly there's been much conflation of plumb and plum over the centuries.
    – Hot Licks
    Commented Jan 9, 2016 at 22:37

The history of the US slang meaning of the word goes back a bit further than the Etymonline explanation. From the OED:


c.B.2.c As an intensive: Completely, entirely, absolutely, quite. Chiefly U.S. slang.

   1587 Misfortunes of Arthur (1828) ii. iv. Chorus 41 Then rowles and reeles and falles at length plum ripe.    1787 Grose Provinc. Gloss., Plum pleasant, very pleasant.    1846 S. F. Smith Theatr. Apprenticeship 213 Long before the time arrived‥the house was plum, chock full—full to overflowing.    a 1861 T. Winthrop John Brent xxviii. 296 When we got here, I paid their tickets plum through to York out of my own belt.    1882 Burdett Life Penn v. 83 Penn‥wrote his wife and children a long letter‥which filled them plumbfull of good advice.    1893 Harper's Weekly Christmas 1211/1 ‘You're plumb crazy’, she remarked, with easy candor.    1897 Kipling Capt. Cour. 21 You've turned up, plain, plumb providential for all concerned.    1901 F. Norris Octopus i. iii. 121 ‘I'll get plumb out of here,’ he trumpeted. ‘I won't stay here another minute.’    1926 ‘R. Crompton’ William—the Conqueror v. 89 Poor woman! She's sure plumb crazy!    1934 A. Christie Murder on Orient Express ii. ix. 136 ‘You are sure of that, M. Hardman?’ ‘I'm plumb certain.’    1967 G. F. Fiennes I tried to run a Railway vii. 76 In his presence I was tense, tongue-tied and often plumb stupid.    1973 E. Lemarchand Let or Hindrance xiv. 182 They must both be plumb crazy.

  • 1
    The 1587 plum ripe looks like a different expression, arising from a comparison with ripe plums falling off a tree. Commented Jun 15, 2011 at 14:12
  • @Peter: I agree. See the second edit to my answer. Commented Jun 15, 2011 at 15:37
  • @Peter: The 1587 usage is still consistent with the meaning "completely," as in "completely ripe." Here's the full text of the quotation: [books.google.com/… Commented Jun 15, 2011 at 16:57
  • It's also quite consistent with the meaning "ripe like a plum," and given the 200-year gap between that and the next occurrence, I don't trust it. Commented Jun 15, 2011 at 17:26

User Callithumpian's answer above states:

Etymonline indicates that the "completely" sense of the word was an extension of the "exact measurement" sense of the word and dates this shift back to the mid-18th

So I thought to enlarge the necessary previous step: how plumb meant "exact measurement". Each indent signifies a response to an earlier post; I omit the usernames for readability.

[Source:] The periodic table's symbol for lead is Pb. Pb comes from the Latin name for lead which is plumbum. Sewage and water pipes used to be made out of lead, hence the occupation of a plumber.

This is also where we get the term plumb to mean vertical or straight down/up - a lead weight at the bottom on a string was used to find the vertical placement of walls or other features.

A plumb bob!


It could come from a number of sources or all of the ones that I list, it is complicated murky history that has never been recorded that I know of.

Logic = 90° to Sane (being level headed) is Insane (Vertical or Straight Up) "Are you Level headed or just Plumb Crazy ?" If you are "around the bend/corner" (90° to being straight headed) then you are Crazy.

Some Plumb Lines used lead weights but many different materials have been used to make the anchor for the line over the centuries. The line must be taught, it is pulled by a weight+gravity, so that it is Square with the Vertical. There are a number of references that can be made from a plumb line to represent Crazy but I will leave that to your imaginations to figure out.

Ok, next is the historical, and stereotype, Crazy Romans link to its usage. Romans were well known for piping clean water supplies into towns from fresh water springs/sources, problem is that they used Lead pipes. The term "Plumber" comes from the Roman lead pipe installers. Next Roman "crazy" health issue was that they used to put lead into wine to make it taste sweeter !!! Lead poisoning makes you go insane because it is a neurotoxin. Aluminum is no better but that wont affect you until you are 60+, it causes long term brain damage in the form of Dementia and other forms of Alzheimer's, you may want to rethink what you use in the kitchen ; )

Modern usage of the Plumb line is an influence of the Romans that used a Groma in surveying. Would not Surprize me at all if the Romans took that from either the Chinese or the Greeks.

There are many colloquialisms in English for being crazy and Plumb Nuts is used but you are more likely to hear local colloquialisms, or current pop culture terms, that are used in various Counties ("States") pending your location on the island. Plumb Crazy does exist in the UK as a saying and a Parliament as proof of it existing as a concept = X D


Plumb is also commonly used in Britain in the phrase the plumb spot, i.e., the best possible position: e.g., in golf, I dropped the ballon the green in the plumb spot to sink it in one, or I've got seats in a plumb spot to see the match. However, it's a bit old fashioned now – tends to be used by middle aged and older people. But, hey, maybe it will come back into fashion again like cool (coined in the 1940s/50s, I believe, by the "hip cats"!).

  • 1
    You may be thinking of plum.
    – MetaEd
    Commented Jan 24, 2012 at 23:53
  • What @MετάEd said. Would Jay speak of landing a plumb job? Commented May 31, 2014 at 20:55

Just an interesting observation: lead causes people to "go crazy", so "plumb crazy" could initially have referred to just that-- the craziness caused by excessive exposure to lead.

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