My research starts here -

"Shave and a haircut,
two bits!" Where did this musical couplet come from, and is there more
to it?

The first recorded occurrence of the tune (with no lyrics) is in an 1899song by Charles Hale, called "At a Darktown Cakewalk." In 1914, JimmieMonaco and Joe McCarthy released a song called "Bum-Diddle-De-Um-Bum,That's It!" in which that line was featured in the last two bars of thesong. In 1939, the same musical phrase was used in a tune called "Shaveand a Haircut - Shampoo" by Dan Shapiro, Lester Lee, and Milton Berle.Somewhere along the line the phrase permutated into "shave and a haircut, bay rum."

Thought that mudcatters could add a bit of story-line here.

voyager