The phrase "tongue in cheek" refers to a style of humor or expression where a statement is intended to be understood as insincere, ironic, or humorous, often suggesting that the speaker is not being serious. This idiom is often used to indicate that what has been said should not be taken literally or seriously, creating a playful or sarcastic tone.
The phrase "tongue in cheek" originated in the 18th century and is believed to refer to the physical act of placing one's tongue against the inside of the cheek as a way to suppress laughter or to convey sarcasm. This gesture has historically been associated with a playful or mockingly insincere expression.