The only free and comprehensive online etymological dictionary of the Spanish language
haz (1) f. (Noun) "face"
10th cent. Old Spanish faz /hadz/. 15th cent. haz. From Vulgar Latin faces "face." From Latin facies "face," "shape." Of unknown origin.
Indo-European
Romance
Portuguese face, Galician face, Catalan faç, French face, Italian faccia, Aromanian fatsã, Romanian fatscha, Sardinian fache

In the 3rd or 4th cent. text Appendix Probi we find the line: facies non fa[ces] "[the word for 'face' is] facies, not faces." The author's spelling correction proves how the word was pronounced by common speakers, and offers a rare glimpse of the evolution of Latin into Romance languages such as Spanish.