late 13c., from Old French toaille (12c.), from Frankish *thwahlja, from Proto-Germanic *thwakhlijon (cf. Old Saxon thwahila, Middle Dutch dwale "towel," Dutch dwaal "altar cloth," Old High German dwehila "towel," German dialectal Zwehle "napkin"); related to German zwagen, Old English þwean "to wash." Spanish toalla, Italian tovaglia are Germanic loan-words.
1836, from towel (n.). Related: Towelled; towelling.
To quit in defeat. The phrase comes from boxing, in which a fighter indicates surrender by throwing a towel into the ring: “After losing the election, he threw in the towel on his political career.”