Pieris was a slave-girl from Aetolia, who though not married to Menelaüs bore him the twins Nicostratus and Megapenthes. As for Pielus, her name means 'rich', 'fat' (pieira), in a literal or metaphorical sense. This same word also meant 'juicy', which although strictly speaking applied to pine-wood could also, one would think, be used of a person.