On
On est un sot = “They-say-so” is half a liar.
[Note that there is no liaison after On here.]
Ongle
Il a de l’esprit jusqu’au bout des ongles = He is witty to the tips of his fingers; He is extremely witty.
Il a bec et ongles = He will fight with beak and claw, tooth and nail.
*Dans les petites boîtes les bons onguents = Small parcels hold fine wares. (See [Aune].)
Il opine du bonnet = He agrees with the previous speakers without saying a word.