Décolleté [da-coal-ta].
Nothing even décolloté should be uttered before ladies—i.e. bearing the least semblance to a double entendre. Décolleté is the French for a “dress cut low about the bosom.”
· 
· 
Entry taken from Dictionary of Phrase and Fable, edited by the Rev. E. Cobham Brewer, LL.D. and revised in 1895.