Where does the phrase “wet blanket” come from and What does it mean?

The term “wet blanket”, one might have supposed, is certainly an example of recent American slang, but it was used in Scotland more than a hundred years ago, and with exactly the meaning in which we use it today, one who puts a damper on anything, especially upon any jollity; one who emits gloom.

The expression was used in 1830 by the Scottish novelist, John Galt, in Lawrie Todd, or the Settlers in the Woods: “I have never felt such a wet blanket before or syne.”

But as this novel contains sketches of American frontier life, the author creates an illusion of American slang.