As stated in the README of the git source code repository, Linus Torvalds came up with the name "git" and said that its meaning depended on your mood. It can stand for:
"global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
"goddamn idiotic truckload of sh*t": when it breaks.
If you want to see for yourself just how accurate this is, just google something like "why do people hate git" and you'll find plenty of funny (and desperate) comments and stories.