Exhausted, worn out, as in This old computer is just about done for. [Colloquial; c. 1800] Also see done in.
Doomed to death or destruction, as in Before he went to the hospital it seemed as if he was done for. [Colloquial; mid-1800s]
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.