Where does “placenta” come from?

placenta (Asturian) comes from Ecclesiastical Latin placenta, from Latin placenta, from Ancient Greek πλακόεντα, from Ancient Greek πλακοῦς, from Ancient Greek πλακόεις, from Ancient Greek πλάξ, from Proto-Hellenic pləks, from Proto-Indo-European pleh₂- — flat.

placenta (Asturian): placenta