The term lounge lizard is usually used to refer to lounge musicians, most often in a pejorative sense. Since its first appearance as American slang in 1917, "lounge lizard" has shown up in nearly every decade.
In Buster Keaton's 1924 film "Sherlock, Jr.", Keaton plays a projectionist at a movie theater where the movie showing is "Hearts & Pearls or The Lounge Lizard's Lost Love". The movie within a movie has a character who is good looking and well dressed who is romantically involved with a wealthy young woman.
A "lounge lizard" is typically depicted as a well-dressed man who frequents the establishments in which the rich gather with the intention of seducing a wealthy woman with his flattery and deceptive charm. The term presumably owes something to the cold and insinuating quality of reptiles.