Old English wyrman "make warm" and wearmian "become warm;" from the root of warm (adj.). Phrase warm the bench is sports jargon first recorded 1907. Warm up (v.) "exercise before an activity" is attested from 1868. In reference to appliances, motors, etc., attested from 1947. Noun phrase warm-up "act or practice of warming up" is recorded from 1915. Related: Warmed; warming.