When there is not much space, a person may say there isn't enough room to swing a cat. The phrase has been used throughout history as a way of saying the room is small or the apartment is small.

That would be the "cat 'o nine tails", a whip used on sailors in the bad old days of sailing ships and press-ganged sailors. As you can imagine, it takes a certain amount of room to get a good back swing on even a relatively short whip, and if there isn't space to get that back swing, there isn't enough room to swing a cat.

About nine feet by nine feet. The expression 'enough room to swing a/the cat' harks back to the space needed, behind the flogger, to accommodate the back-swing the cat-of-nine-tails lash that was used to flog sailors, back in the day

No room to swing a cat referers to a very small area.