For my homebrew it is Hauflin. It literally translates to "all family" (hauf + lin) in their native tongue. They will also say "the Lin", if they are being quick, which they usually are not.
It was corrupted to Haflin by the Dwarfs. When Humans heard it, they changed it yet again, to Halfling. The reason was two fold. First, Humans assumed the Dwarfs dropped the 'g' from the end of the word, as they are want to do. Second, it seemed to 'fit', based on the little ones size.
Most Halflings don't care enough to correct any of the Big Folk.