Q: Where does the expression “tongue and cheek” come from?
A: The theory, though there’s not much evidence to support it, is that the phrase “tongue in cheek” comes from the practice of sticking your tongue in your cheek (thus making a bulge in your cheek) to keep from laughing. It originated in the 18th century and now is used to refer to something said facetiously or ironically. Example: “Ralph offhandedly stuck his arm in the garbage disposal,” said Tom, tongue in cheek.
Note that it’s not “tongue AND cheek.”