"dried, twisted intestines used for strings of musical instruments," 1590s, perhaps altered from *kitgut, and from obsolete kit (n.2) "fiddle" + gut (n.). It was made from the intestines of sheep, not cats.

"pool of money in a card game," 1884, American English, of uncertain origin. OED connects it with kit (n.1) in the 19c. sense of "collection of necessary supplies;" but perhaps it is rather from northern England slang kitty "prison, jail, lock-up" (1825), a word itself of uncertain origin.

By the Widow, or as it is more commonly known as "Kitty," is meant a percentage, taken in chips at certain occasions during the game of Poker. This percentage may be put to the account of the club where the game is being played, and defrays the cost of cards, use of chips, gas, attendance, etc. The Kitty may, however, be introduced when no expenses occur. ["The Standard Hoyle," New York, 1887]

name of a club founded by Whig politicians in London (Addison and Steele were members), 1703; so called from Christopher ("Kit") Catling, or a name similar to it, a tavernkeeper or pastry cook in London, in whose property the club first met. Hence "a size of portrait less than half length in which a hand may be shown" (1754), supposedly is because the dining room in which portraits of club members hung was too low for half-length portraits.

"subsequent assembly of something bought in kit form" (furniture, etc.), by 1966; see self- + assembly.