den of iniquity

Etymology:

• 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." The origin of the phrase "den of iniquity" is unclear. It becomes common in American writing of the 1940s.