Slutstitue is an accepted denotative meaning of a sexually promiscuous woman that is known to be a dirty piarte hooker, yet still maintains a common placement among a group atmosphere.
Slut is a pejorative term for a sexually promiscuous person (usually females), more than is deemed socially acceptable.
The term is interchangeable with prostitute as this term denotes a person who engages in sex for money, or other services and companionships to which they find of value.
You want to get paid but you don't, it's a word that can be anything we want since it's drived names are slut = self defining and prostitute, which means getting paid for sexual favours so that makes a prostitute a slut.
Therefore we create a new word for prostitute and make it slutstitute.