C’est vieux comme le Pont Neuf = Queen Anne is dead; It is as old as the hills.
[The Pont Neuf was finished in 1604 during the reign of Henry IV., and is now the oldest bridge in Paris. The statue of Henry IV. in the middle of the bridge was erected originally in 1635, but the present one dates only from 1818.
Another expression is:
Henri Quatre est sur le Pont Neuf = That’s stale news.]
Pontoise
Il a l’air de revenir de Pontoise = He looks down in the mouth; He answers in a silly fashion.
[The origin of this expression is said to be that in 1720 and in 1753 the Parlement was exiled to Pontoise, about twenty miles north of Paris, for its rebellion to the King. Perhaps from the fact that when they returned they were besieged with questions, to which they gave confused answers, the saying arose and was applied to anyone that had a simple, idiotic appearance.]
Ils ont mis la clef sous la porte = They absconded.
Il faut qu’une porte soit ouverte ou fermée = You must decide one way or the other.
[The title of one of Alfred de Musset’s Proverbes.]