From charlatan + -ism.

charlatanism

1. (uncountable) The state of being a charlatan
   • 1861, Benjamin Ridge, Ourselves, Our Food, and Our Physic:

     It will cure by science and philosophy instead of empiricism, and will deal the deadliest blow to charlatanism.

2. (countable) An act of a charlatan

• charlatanerie
• charlatanry
• quackery