Meaning of the word "by the by" in English

What does "by the by" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

by the by

US /baɪ ðə baɪ/
UK /baɪ ðə baɪ/

Idiom

incidentally; by the way

Example:
By the by, have you heard from Sarah recently?
Oh, by the by, I found your lost keys.