What is a baw hum?

"Baw hum" is not a recognized phrase or term. It's likely a misspelling or a humorous alteration of a common phrase.

Do you mean:

* Bah humbug! - This is a famous exclamation from the Charles Dickens novel "A Christmas Carol" used to express disdain for Christmas and its traditions.

* Bah! Humbug! - This is a more accurate way to spell the phrase.

* Bah humbug! - This is a variation of the phrase used to express general cynicism or annoyance.

If you had something else in mind, please provide more context or information.