Idiotism

noun

1. An idiom; a peculiarity of phrase; a current deviation or departure from the strict syntactical rules or usages of a language.
2. A personal peculiarity of expression.
3. Idiocy; the state of being an idiot.
4. An idiom; a form, mode of expression, or signification, peculiar to a language.
5. Lack of knowledge or mental capacity; idiocy; foolishness.