before 900; (adj.) Middle Englishwerm, warm,Old Englishwearm; cognate with Germanwarm,Old Norsevarmr; (v.) Middle Englishwarmen, wermen,Old Englishwerman, wirman (transitive), wearmian (intransitive), both akin to the adj.; (noun) derivative of the v.
O.E. wearm, from P.Gmc. *warmaz (cf. O.S., O.Fris., M.Du., O.H.G., Ger. warm, O.N. varmr, Goth. warmjan "to warm"), from PIE *gwher- (cf. Skt. gharmah "heat;" O.Pers. Garmapada-, name of the fourth month, corresponding to June/July, from garma- "heat;" Arm. jerm "warm;" Gk. thermos "warm;" L. formus "warm," fornax "oven;" O.Ir. fogeir "heated;" Hitt. war- "to burn"). The root also may be connected to that of O.C.S. goriti "to burn," varu "heat," variti "to cook, boil;" and Lith. verdu "to seethe." The distinction, based on degree of heat, between "warm" and "hot" is general in Balto-Slavic and Gmc., but in other languages one word often covers both (cf. L. calidus, Gk. thermos, Fr. chaud, Sp. caliente). In reference to feelings, etc., attested from c.1480. Sense in guessing games first recorded 1860, from earlier hunting use in reference to scent or trail (1713). Warm-blooded in ref. to mammals is recorded from 1793. Warm-hearted first recorded c.1500.
O.E. 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 ref. to appliances, motors, etc., attested from 1947. Noun phrase warm-up "act or practice of warming up" is recorded from 1915.