(From a post by Major Dick Culver of “Culver’s Shooting Pages)

CAT O’NINE-TAILS:

A short nine tailed “flailing device� used to administer corporal punishment in the sailing ship days. The “Cat� was kept in a red velvet-like bag to conceal the blood drawn during punishment. Hence the term, “when The Cat’s out of the Bag�, punishment is imminent or in more modern times; the term “Uh Oh, someone’s found us out!� (and left unsaid was “and we’re probably gonna’ get punished�) is derived from the old “Cat O’Nine Tails� caution…

~ AND A VARIATION ~

“NOT ENOUGH ROOM TO SWING A CAT�:

As above, when mentioning “letting the cat out of the bag� they were referring the “cat o’nine tails� or a flail with lead balls on the end of rawhide lashes used to administer punishment aboard ship! Thus when punishment was to be administered, the cat came (or WAS) out of the bag. The saying there’s “not enough room to swing a cat� has reference to the same implement of torture. If there wasn’t enough room to “swing a cat� (o’nine-tails of course), the room or space was very small indeed.