The only free and comprehensive online etymological dictionary of the Spanish language
caballero m. (Noun, Adjective) "gentleman," "cowboy," "knight;" "gentlemanly"
11th cent. From Late Latin caballarius "horseman," from Latin caballus "horse" (whence caballo) and -arius, an agent-forming suffix (see -ero).
Also the origin of the surnames Caballero, Caballeros.
Indo-European
Romance
Asturian caballeru, Portuguese cavaleiro, Galician cabaleiro, Catalan cavaller, French chevalier, Italian cavaliere, Romanian cavaler, Sardinian cabaglieri