sub rosa
MEANING:
adverb: Secretly, privately, or confidentially.
ETYMOLOGY:
From Latin sub (under) rosa (rose). Earliest documented use: 1654. The English term "under the rose" is also used to refer to something in secret.
NOTES:
In Roman mythology, Venus's son Cupid gave a rose to Harpocrates, the god of silence, to ensure his silence about Venus's many indiscretions. Thus the flower became a symbol of secrecy. Ceilings of banquet halls were decorated with roses to indicate that what was said sub vino (under the influence of wine) was also sub rosa.