mid-13c., from Old French toaille (12c.), from Frankish *thwahlja, from Proto-Germanic *thwahlijan (source also of 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. To throw in the towel "admit defeat" (1915) is from boxing.
1836 (transitive); 1861 (intransitive), from towel (n.). Related: Towelled; towelling.