by the by/bye

by the by

Incidentally; on a side note; by the way. An interjection meant to casually introduce or emphasize additional information in the conversation. Sometimes, though less commonly, written as "by the bye." By the by, I remembered where I left my keys, in case you were wondering. Beckett was an amazing playwright. There's a lecture on his work tomorrow, by the by.
See also: by
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.

by the by/bye

By the way, incidentally, as in “By the by, I saw your brother there as well.” The second by or bye in this archaic-sounding cliché originally denoted a side path, whence the current sense of “in passing.”
See also: by, bye
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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