in strict confidence

1 秘密

tête-à-tête hugger-mugger close inside private secret interior hidden underground closet mysterious confidential sneak undercover backstage esoteric privy cryptic clandestine backdoor stealthy backroom underhanded underhand closed-door sneaking surreptitious hush-hush under-the-table unavowed back-street undivulged huggermugger hole-and-corner backstair secretly darkly confidentially surreptitiously cryptically secretively privily unavowedly privacy confidence mystery darkness confidentiality stealth secrecy QT secretiveness arcanum re- hide on the qt in petto under the rose under hat sub rosa under cover behind closed doors in confidence through the back door by the back door

2 秘密地

underground secretly backstage darkly confidentially surreptitiously underhand cryptically secretively privily huggermugger unavowedly on the qt under the rose under hat sub rosa under cover behind closed doors in confidence through the back door by the back door