For me, charlatan is a whimsical and particularly satisfying way to insult people in a joking manner. To a person living in Shakespearean England, however, it referred to a person who sold faulty remedies (an even more old-timey snake oil salesman, in short). This was borrowed from exactly the same word in Middle French, although then meaning something more like "swindler" in general. In Old Italian, it was ciarlatano, and here it gets it gets interesting: because these sneaky tricksters talked a lot, this comes from the verb ciarlare, meaning "to babble" (or, in noun form, ciarla, "chat"). Now, Italians are traditionally stereotyped as being very active talkers, but even among the Italians, the general consensus was that people from a village called Cerreto in the Umbria region babbled the most (they also had a lot of proverbial charlatans), so we can trace ciarla to the name for that town. Peak usage of the word charlatan was surprisingly in the 1930s (encompassing about 0.00007% of all words written), but in recent years it has thankfully started an uptick again. Lot of charlatans out there!
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.