I know some people who can fall asleep pretty fast, but the term "fast asleep" doesn't seem to mean that. When I looked it up, all it showed was "someone sleeping tightly". How did fast come to be associated with sleeping?


The etymonline entry for fast says:

fast (adj.)
Old English fæst “firmly fixed, steadfast, secure, enclosed”, probably from Proto-Germanic fastuz, from PIE base past- (firm). The adverb meaning “quickly, swiftly” was perhaps in Old English, or from Old Norse fast, either way developing from the sense of “firmly, strongly, vigorously” (cf. to run hard means to run fast; also compare fast asleep)

It has a close meaning of “firmly, strongly” in “the box was strapped fast to the truck”, and as an adjective in “fast dye” (not fading) or “fast friend” (close).

  • 1
    +1 -- the same etymology applies to the German term "fest schlafen", and "fest" means "firmly, strongly" in German. It's interesting to see that in this turn of phrase, "fast" has nothing to do with speed.
    – teylyn
    May 13 '11 at 11:03
  • 2
    Nautical to "make fast" is to tie securely, as a boat to a slip or dock. May 13 '11 at 12:46
  • 1
    +1 and of course German festhalten (hold tight) @teylyn ! May 14 '11 at 3:04
  • also "steadfast" and "handfasting" retain this meaning today. Sailors sometimes say "make it fast" to mean "tie it up". It's just one of those words that has two meanings that happen to be near-opposites. May 14 '11 at 12:29

In order to be 'fast asleep' the meaning of the word "fast" has to be defined.

"fast" (as already defined above) means "tight, safe, secure".

Hence, the phrase "fast asleep" basically means the same as 'sleep tight. But that still doesn't answer the question. So these two phrases mean the same thing, but what caused these phrases to come about?

Looking into history, the beds of last time were basically frames elevated from the ground with ropes tied in a kind of web underneath the mattress. In order to have a comfortable night, the ropes have to be tight. Hence, the expression,"Sleep tight!" And from that, the expression "fast asleep" was most probably derived.


  • I was wondering if someone would mention the sleep tight etymology, always interesting.
    – Orbling
    May 14 '11 at 2:35
  • Yes, very indeed. Interestingly, in the series Little House on the prairie, the beds I noticed actually were made of 'elevated frames with ropes tied across in a type of web'
    – Thursagen
    May 14 '11 at 2:37
  • Well, before sprung mattresses, that was about the best suspension you were going to get!
    – Orbling
    May 14 '11 at 8:12
  • Just want to point out that the first explanation in Straight Dope was mostly a joke; to "sleep tight", like to be "fast asleep", just means that sleep has you "tightly" in its grip. Jul 10 '11 at 17:13

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