Money-laundering is the act often associated with criminals who want to 'clean' their ill-obtained gains, and recirculate it into the legal economy, so that they can use such wealth without raising eyebrows.

Hence the term which refers to the money being 'laundered', so to speak.

It usually involves circuitous routes by which the money is injected back into the legal economy. Such money is disguised, either as returns from often dubious investments or through fictitious sales of retail outlets that act as fronts for the criminal enterprises involved.