...the origin of "sub rosa"...are at least partly shrouded in obscurity and confusion. According to one of my reference books ("From Achilles' Heel to Zeus's Shield," by Dale Corey Dibbley), the whole story was pretty much invented by the Romans. According to the myth, one fine afternoon a child god named Harpocrates stumbled upon the goddess Venus while she was engaged in one of her many illicit rendezvous. Venus's son Cupid, who happened to be in the neighborhood as well, quick-wittedly saved his mother's reputation by offering Harpocrates a beautiful rose in return for his vow of silence. Harpocrates kept his mouth shut, and the rose thereafter became the symbol of silence.For a minor Roman myth, this one had legs, as they say in show biz. It was still common in Medieval times to see a rose suspended over a dining table in France and England to remind guests that conversations at the table were not to be repeated elsewhere. Eventually real roses were replaced by plaster ones, and roses were still commonly found in the plaster work in many Victorian dining rooms. Today, "sub rosa" (and, less often, "under the rose") is a synonym for "secret," with the added connotation of "illicit."