The only free and comprehensive online etymological dictionary of the Spanish language
caballo (Noun) "horse"

10th cent. From Latin caballus 'id.' Of non-Indo-European origin. Borrowed from an unknown language from 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.

Romance: Western Vulgar Latin: Asturian caballu, Portuguese cavalo, Galician cabalo, Catalan cavall, French cheval, Italian cavallo; Eastern Vulgar Latin: Aromanian cal, Romanian cal; Sardinian cadhu; Extra-Comparanda: Albanian kalë

Hellenic: Ancient Greek καβάλλιον (kabállion) "workhorse"