idiotism1

[id-ee-uh-tiz-uh m] /ˈɪd i əˌtɪz əm/
noun
1.
idiotic conduct or action.
2.
Origin
1585-95; idiot + -ism

idiotism2

[id-ee-uh-tiz-uh m] /ˈɪd i əˌtɪz əm/
noun, Obsolete
1.
an idiom.
Origin
1580-90; < Latin idiōtismus < Greek idiōtismós a vulgar phrase, peculiar way of speaking
British Dictionary definitions for idiotism

idiotism

/ˈɪdɪəˌtɪzəm/
noun
1.
an archaic word for idiocy
2.
an obsolete word for idiom