a secret dungeon with an opening only in the ceiling, as in certain old castles.
1810-20; < French,Middle French, equivalent to oubli(er) to forget, Old Frenchoblider < Vulgar Latin*oblītāre, derivative of Latinoblītus (past participle of oblīvīscī to forget; see oblivion) + Middle French-ette-ette
"secret dungeon reached only via trapdoor," 1819, from Fr. oubliette (14c.), from M.Fr. oublier "to forget," from O.Fr. oblider, from V.L. *oblitare, from L. oblitus, pp. of oblivisci "to forget" (see oblivion).