1) Latin for "thirsting."
2) According to the Clark County News of December 1875, it is a disease "caused from people sitting around too much and taking no exercise."
3) A palindrome that just happens to have the words "sit," "it," "tit," and "'tis" in it.
Laura, if you keep telling me to sit tight, I’m gonna get a bad case of sititis!
Urkel, if you don’t stop complaining you’ll get a worse case of broken-face-and-glasses!
–Family Matters, Episode 88