IDIOTISM
Etymology 1
Noun
idiotism (countable and uncountable, plural idiotisms)
(now, chiefly, historical) Very severe mental retardation.
A foolish utterance.
Etymology 2
Noun
idiotism (plural idiotisms)
Idiom.
An overly literal translation of an idiom.
Source: Wiktionary
Id"i*ot*ism, n. Etym: [F. idiotisme, L. idiotismus the way of fashion
of a private person, the common or vulgar manner of speaking, Gr.
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.
Source: Webster’s Unabridged Dictionary 1913 Edition