Spanish word perro comes from Proto-Indo-European *ḱwṓ (Dog.)
*ḱwṓ (Proto-Indo-European)
Dog.
*kō (Proto-Italic)
canes (Latin)
canis (Latin)
A dog (animal). A dog (foul person).
can (Spanish)
Dog, hound.
perro (Spanish)
Awful. Doggy, doggish. Wicked, mean Dog.