Idiotism /(?)/

Id·i·ot·ism

Idiotism

n.
  1. An idiom; a form, mode of expression, or signification, peculiar to a language.
    Scholars sometimes give terminations and idiotisms, suitable to their native language, unto words newly invented.
    — M. Hale.
  2. Lack of knowledge or mental capacity; idiocy; foolishness.
    Worse than mere ignorance or idiotism.
    — Shaftesbury.
    The running that adventure is the greatist idiotism.