On Wikipedia we read:
dirty money: (idiomatic) Money that is illegally gained, illegally
transferred or illegally utilized. Especially money gained through
forgery, bribery, or thievery.
Is there a precise origin of the idiom "dirty money"? Why has the word "dirty" replaced "illegal"? (perhaps because an author has used it an important novel?)
Best Answer
The OED specifically traces the term "dirty money" to a source over a century old:
Yet for some time, dirty has been applied to more than our dirty socks, or a muddy shirt. Dirty has been used to convey sullied, tainted, impure, corrupt, illicit, immoral, etc.
The OED lists such nuances among its several meanings for dirty:
With that kind of heritage for the word dirty, it's not a long leap to apply the word dirty to ill-gotten funds.
As a side note, in addition to dirty money, the OED doesn't forget or neglect dirty pool, dirty words, dirty tricks, and dirty old men.