From Middle English forspenden, from Old English forspendan (“to spend up, give out, squander, consume”), equivalent to for- + spend.
forspend (third-person singular simple present forspends, present participle forspending, simple past and past participle forspent)
- (transitive) To spend up; spend completely; exhaust, as by overexertion.
- a painful march, Through twenty hours of night and day prolong'd, Forspent the British troops. ― Southey.