10th cent. From Latin caballus 'id.'
Of non-Indo-European origin. Borrowed from an unknown language in Asia with the root *kab- (compare Turkish käväl "horse;" Russian kobýla "mare;" Old Church Slavonic koņь "horse"). Further consider Semitic words for camel with a structure *gam- (Hebrew gāmāl), hypothesized to be borrowed from an unattested Sumerian word.
Also the origin of the surnames Caballero, Caballeros, first given to horsemongers.
Asturian caballu, Portuguese cavalo, Galician cabalo, Catalan cavall, French cheval, Italian cavallo, Aromanian cal, Romanian cal, Sardinian cadhu
Ancient Greek καβάλλιον (kabállion) "workhorse"