not enough room to swing a cat

Attested 1665, by which point already in common use; perhaps of naval slang origin.

While it is frequently stated that the phrase is derived from cat-o’-nine-tails (“type of whip”),[1] this latter term is only attested from 1695, and hence this idiom presumably derived from literally swinging a cat around, as by the tail.[2]

not enough room to swing a cat (uncountable)

1. (informal) Very little space (available) (of a very small room).
   • 1665, Richard Kephale Medela Pestilentiae[2]

     They had not space enough (according to the vulgar saying) to swing a Cat in.

   • 1960, P. G. Wodehouse, Jeeves in the Offing, chapter VIII:

     My own apartment, to take a case in point, was a sort of hermit's cell in which one would have been hard put to it to swing a cat, even a smaller one than Augustus, not of course that one often wants to do much cat-swinging.

Not widely used in 21st century American English.

• confined, cramped, tiny