Told sub rosa

Told sub rosa (under the rose) Anything told sub rosa (under the rose) is spoken in strictest confidence and must not be repeated.
The rose in question is the white rose which has for long been the emblem of silence.

Whenever a white rose was hung above the banqueting table, no matter what was said or whatever the company, no secrets revealed were ever to be repeated. The custom originated with the Romans and spread to England, where it was widely used during the days of chivalry. It persisted until Victorian times when the living rose was replaced by a plaster motif carved in the ceilings of dining-rooms, many of which can still be seen today.