RichThesaurus
empty-headed
vs
two sandwiches short of a picnic
empty-headed
adj
Silly and lacking sense or discretion; featherbrained or scatterbrained.
two sandwiches short of a picnic
How often have the words
empty-headed
and
two sandwiches short of a picnic
occurred in a corpus of books?
(source:
Google Ngram Viewer
)