A term traditionally used by hicks to encourage others to finish a chore or task, or some other thing. Larry the Cable Guy puts it into other light; the term "gidderdun" in the new day and age means "ALRIGHTTTT!"
1) "didja finish your cornmeal? well, gidderdun!"
2) "Ya, so I told the police chief to shut the fuck up! hahaha, ahh... GIDDERDUN!"