\Id"i*ot*ism\, n. [F. idiotisme, L. idiotismus the way
of fashion of a private person, the common or vulgar manner
of speaking, Gr. ?, fr. ? to put into or use common language,
fr. ?. See {Idiot}.]
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.
                                               --Hammond.