Although many charlatans are proper charlies (which is British for silly fools) the words charlie and charlatan don't have anything to do with each other.
Charlie in this sense is British rhyming slang (there's an Australian rhyming slang charlie, too, which means female person) but charlatan is French.
That's why you say charlatan with a sh sound: SHARLaT'N.
A charlatan is a cheat who sets himself up as an expert and then sells his so-called knowledge.
A charlatan painted by Hieronymous Bosch
A charlatan often pretends to have medical knowledge - the original charlatans in France sold fake medicines with the help of outdoor stage shows - but he can pretend to know about anything.
The universe working the way it does, a charlatan usually pretends to know about the future.
A charlatan will be gifted in his ability to sway the minds of many people, and to convince them of many things.
He'll be a great promiser; he will seem hugely confident; and most of all he will seem trustworthy.
Given a credulous audience, he can do an awful lot of damage, too.
Word To Use Today: charlatan. The word charlatan is French. Before that it comes either from ciarlare, an Italian word meaning to chatter, or perhaps from Cerretano, someone from Cerreto, which is a village in Umbria previously known for its quacks.