Synonyms for By the bye:
adv
•by chance (adverb)incidentally.
adv.
•all (adverb)by the way, incidentally.
•by the way (adverb)
incidentally.
•incidentally (adverb)
by the way.
n.
•by the bye (noun)by the way, incidentally.
Other synonyms:
•adv
by the way.