- backdoor (adj.)
[backdoor 词源字典]
- also back-door, "devious, shady, illegal," 1640s. The notion is of business done out of public view. The noun back door in the literal sense is from 1520s, from back (adj.) + door. The association with sodomy is at least from 19c.; compare also back-door man "a married woman's lover," black slang, early 20c.[backdoor etymology, backdoor origin, 英语词源]