If I could work my will," said Scrooge indignantly, "Every idiot who goes about with 'Merry Christmas' on his lips, should be boiled with his own pudding, and buried with a stake of holly through his heart.
For Scrooge (and Scrooge McDuck!) Christmas is 'humbug' - a fraudulent commercial trick aimed at 'picking a man's pocket'. ‘Bah!’ said Scrooge, ‘Humbug! What’s Christmas time to you but a time for paying bills without money? For finding yourself a year older, but not an hour richer?’ But what is humbug? In general English 'humbug' describes insincere or hypocritical speech - Scrooge accuses all around him of only pretending to be interested in the plight of the poor.
In British English, a striped candy/sweet. It's boiled and hard enough to crack a tooth. Dentists cry, 'Bah! Humbug! - all the way to the bank. More on A Christmas Carol