noun, masculine/sə.kʁɛ d(ə) pɔ.li.ʃi.nɛl/plural: secrets de Polichinelle
open secret, secret of Polichinelle
“A six mois du scrutin municipal demeurent quelques secrets de Polichinelle dans la capitale comtadine.”
Literally, “secret of Polichinelle”, from a play of the same name by Pierre Wolff (1903), about a bourgeois family trying to conceal the “open secret” that their married son has a child born out of wedlock.