Q: When we played tic tac toe as children, we would refer to a tie game as a "cat." How did it get that name?
A: It's hard to find a central reason behind this one. I found sources that present several theories. A good rundown of them is on the website gameskidsplay.net.
One theory is tac spelled backward is cat. Another is, a tie is considered "scratch game," and cats are known for scratching.
A third notion is that tic tac toe is a "cat and mouse" game. If it ends in a tie, nobody "got away" with the win, which means the mouse did not get away from the cat, so it's the cat's game. If someone "gets away" with winning, the mouse escaped.
Another theory claims when a game ends in a tie, the Xs or Os often form a half circle resembling a c, for cat. Along those lines, one suggestion is the half circle resembles a cat's tail curled up.
This question caused me to wonder about the origin of the name tic tac toe. In looking for the answer, I came across an interesting website from the University of California, gamescrafters.berkeley.edu.
The site belongs to the UC Berkeley GamesCrafters, who explore game theory. They have a project called GAMESMAN, which is "a system developed for solving, playing and analyzing two-person, abstract strategy games," according to the site.
The site explains tic tac toe originally was called tit tat toe in the 1500s, with tit meaning to slap and a tit for tat referring to retaliation. Toe is the third piece that makes the winning combination when matched with the other two pieces.
By the way, the site mentions a version of the game called "two-part tit-tat-toe." In it, each player places three pieces on the tic tac toe board. The two players take turns moving a piece to an empty square in an attempt to form three in a row. Like tic tac toe, the game can end in a stalemate.
There also is "two-part tit-tat-toe with jumps," which is like two-part tit-tat-toe but, as the name suggests, you can jump another player's piece and land on an adjacent empty square.
Then there's "three-dimensional tit-tat-toe," which involves three boards drawn on top of each other, and players try to make three in a row on any one grid or through the grids.