The only free and comprehensive online etymological dictionary of the Spanish language
cabeza f. (Noun) "head"
10th cent. From Vulgar Latin *capitia 'id.,' from caput "head" (see cabo) and -itia, an abstract noun-forming suffix (see -eza).
Also the origin of the surname Cabezas, first applied as a nickname to local leaders known for their intelligence.
Asturian cabeza, Portuguese cabeça, Galician cabeza, Catalan cabeç, French chevet, Italian cavezza

Western Vulgar Latin reanalyzed the neuter plural as a feminine singular noun (see arma and hoja).