Polyxo was the name of at least three women. One was a prophetess who was an old nurse of queen Hypsipyle, another was the widow of Heracles' son Tlepolemus, and a third was the mother of Antiope by Nycteus.
The name seems to be a contraction of 'Polylyxo' and thus means 'much light', from polys, 'much' and lyce, 'light'. Robert Graves, however, derives it from polys and xyo, 'to scrape', so that it means 'much itching'. But in what precise sense - there's the rub.