The headword phrase, unglossed, is also in Photius.
Deriving from a courtroom witticism in Lysias, In reply to Aischines the Socratic. See the long extract preserved in Athenaeus, Deipnosophists 13.611E-612F (13.95 Kaibel), at 612F, of a 70-year-old woman there, whose teeth were fewer than the fingers of one hand.