under the rose in confidence; under pledge of secrecy. archaic

☞ The origin of the rose as an emblem of secrecy is uncertain; the concept may have originated in Germany and there was a similar expression in early modern Dutch. Under the rosse appears in a 1546 State Paper of Henry VIII, with a gloss that suggests that it was then a new or unfamiliar expression. The Latin equivalent sub rosa has also been very commonly used in English since the mid 17th century in this metaphorical sense.