charlatan (n.)

From the Online Etymology Dictionary:

“one who pretends to knowledge, skill, importance, etc.,” 1610s, from French charlatan “mountebank, babbler” (16c.), from Italian ciarlatano “a quack,” from ciarlare “to prate, babble,” from ciarla “chat, prattle,” which is perhaps imitative of ducks’ quacking. Related: Charlatanical.

charlatanism (n.)

“methods of a charlatan,” 1804, from French charlatanisme; see charlatan + -ism. OED describes synonym charlatanry(1630s) as “More contemptuous … and referring more to actual practice.”