The term "humbug" in western culture now exclusively refers to its use to insult a "negative Nancy." Most think the term is derived from a nonsense word used by Ebenezer Scrooge in Dickens' "A Christmas Carol," published in 1943. "Our Mutual Friend" was published twenty-one years later in 1964. The use of the term here could indicate that the novel was so successful that it found its way into the common vernacular, but is also a funny way to self-promote his other works. The actual roots of humbug are found in 1751.

https://www.scientificamerican.com/article/cognitive-ability-and-vulnerability-to-fake-news/