den of iniquity
The term "iniquity" ultimately derives from Latin aequus, meaning equal, plus the negative in- meaning "not". Though apparently very similar to "inequity", which refers to injustice or unfairness,"iniquity" has a strong negative moral implication. It refers to acts regarded as sinful or depraved. The notion of a "den" as a place where dangerous or illicit activities are carried out can be traced back to the King James version of the Bible. In both Gospel of Mark and Matthew, Jesus condemns those who have been using the sacred temple as a marketplace, proclaiming that they have "made it a den of thieves." [See also "Daniel in the lion's den."] The origin of the phrase "den of iniquity" is unclear. It becomes common in American writing of the 1940s.
- (idiomatic) A place of immoral behavior, usually of a sexual type.
The song "In Our Little Den of Iniquity" from the 1940s musical "Pal Joey" is an example. It refers to a secret hideaway for romantic rendezvous. Used more solemnly, the expression "den of iniquity" implies a certain discernment that a morally upright person would consider intolerable. There are several earlier (19th century) examples viewable on the Making of America websites, such as this one from an 1840 book by George E. Dabney: "The young men made their preparations with alacrity, and, headed by this western patriarch, we proceeded at a rapid gait to surprize the tenants of this den of iniquity."