RichThesaurus
daft as a brush
vs
non compos mentis
daft as a brush
adj
Tending to do or say silly things.
non compos mentis
adj
Insane; not of sound mind; not in control of oneself.
How often have the words
daft as a brush
and
non compos mentis
occurred in a corpus of books?
(source:
Google Ngram Viewer
)