RichThesaurus
off and on
vs
once in a blue moon
off and on
adv
On different tacks, now toward, and now away from, the land.
once in a blue moon
adv
Very rarely; very infrequently.
How often have the words
off and on
and
once in a blue moon
occurred in a corpus of books?
(source:
Google Ngram Viewer
)