Adverb

1. Incidentally; a parenthetical statement not timely, central, or crucial to the topic at hand; foregone, passed by, something that has already happened.

   • His mother will be coming for dinner tomorrow, and, by the way, she volunteered to bring dessert.

   1853 Melville, Herman Bartleby, the Scrivener, in Billy Budd, Sailor and Other Stories, New York: Penguin Books, 1968; reprint 1995 as Bartleby, ISBN 0 14 60.0012 9, p.2:

   • [...] I had counted on a life-lease of the profits, whereas I only received those of a few short years. But this is by the way.