What does ba humbug mean?

a “humbug” is something false or deceitful (like the Wizard of Oz being the little man behind the curtain). so “Bah! is an out burst, and “bah, humbug!” was Scrooge’s expression that Christmas cheer was false.

The reference above to Scrooge is a reference to Charles Dickens’s classic Christmas tale A Christmas Carol. Scrooge is a bitter old miser who thinks Christmas is meaningless. He is visited in the night by ghosts who teach him the true spirit of Christmas. Here is an excerpt from the beginning, with this expression in it:

————

“A merry Christmas, uncle! God save you!” cried a cheerful voice. It was the voice of Scrooge’s nephew, who came upon him so quickly that this was the first intimation he had of his approach.

“Bah!” said Scrooge, “Humbug!”

He had so heated himself with rapid walking in the fog and frost, this nephew of Scrooge’s, that he was all in a glow; his face was ruddy and handsome; his eyes sparkled, and his breath smoked again.

“Christmas a humbug, uncle!” said Scrooge’s nephew. “You don’t mean that, I am sure.”

“I do,” said Scrooge. “Merry Christmas! What right have you to be merry? What reason have you to be merry? You’re poor enough.”

“Come, then,” returned the nephew gaily. “What right have you to be dismal? What reason have you to be morose? You’re rich enough.”

Scrooge having no better answer ready on the spur of the moment, said “Bah!” again; and followed it up with “Humbug.”

I think it means “ah fuck it” “who cares”. Just plain and simple.

No, it doesn’t, @Inked_up_chic. It’s a direct literary reference, and it pertains to Christmas in particular.

I lurve you @Jeruba!

Bah is an exclamation meaning phooey
It could also be a precursor of the ghost since bug meant ghost in Middle English, and to hum was to lie.
Humbug means hoax or fraud

^^^ ...thus illustrating that the whole is greater than the sum of its parts. Each individual term (“bah” and “humbug”) has its own meaning and history, but when you pair them in this familiar expression, the new term (“Bah! Humbug!”) has a single context of origin and a single import.

@jeruba Dickens may be the popularising source, but “Bah! Humbug” means a disinclination to join in with received wisdom regarding the fun/joy of an event or such like. It will be said an awful lot regarding the forthcoming wedding of William Windsor and Kate Middleton.

The meaning of “Bah! Humbug!” is closer to saying “what a joke!”