Where does “cuatro” come from?

cuatro (Spanish) comes from Old Spanish quatro, from Latin quattŭor, from Portuguese quarto, from Old Portuguese quarto, from Latin quārtus, from Proto-Indo-European kʷeturtos, from Proto-Indo-European kʷetwóres, from Proto-Indo-European kʷe- — and.

cuatro (Spanish): four; A four-stringed guitar with the first...