What Does the Common Idiom Tongue-in-cheek Really Mean?

Meaning of tongue-in-cheek
Very often you must have experienced your friend, colleague, or family member make a comment on something or say something with a neutral look on their face, later only to burst out laughing. Well, the comment is nothing but a tongue-in-cheek statement. But what does tongue-in-cheek exactly mean?
Did You Know?
Sir Walter Scott used tongue-in-cheek idiom in the year 1828 in his novel The Fair Maid of Perth as:"The fellow who gave this all-hail thrust his tongue in his cheek to some scapegraces like himself."
There you are having a conversation with your friends, when your friend's expression suddenly changes and she says something like, "I don't want to be friends with you anymore." You stand there dumbfounded not understanding what to say. But then she starts laughing. Of course, your good old friend couldn't hold her tongue in her cheek for a long time. We come across such situations many times in our daily life.
Tongue-in-cheek is a figure of speech used, which in simplest terms means a speaker is pretending to be serious while saying something funny. We generally try to hold back our smile or laugh by pushing our tongue against our cheek to sound serious. If you force your tongue against your cheek you won't be in a position to smile or even talk. Your tongue-in-cheek demeanor thus means that you're joking, although you may pull a stern face.
This type of witticism is ironic and sometimes difficult to catch as compared to the other obvious forms of humor. British culture enjoys and promotes such humor in the form of movies, plays, and jokes. One of the signs of tongue-in-cheek joke is when a person winks right after making a comment. In the upcoming sections, we will learn more about this idiom's history, and tongue in cheek examples.
Origin of Tongue-In-Cheek
While much is not known about the history of this proverb, earlier it was employed to indicate contempt, however that is no longer the meaning.

In the novel, The Adventures of Roderick Random published in the year 1748 by Tobias George Smollett, the eponymous hero is traveling in a coach to Bath. There he arrests a highwayman which leads to an argument with a passenger. The hero stated, "He looked back and pronounced with a faltering voice, 'O! 'tis very well-damn my blood! I shall find a time.' I signified my contempt of him by thrusting my tongue in my cheek, which humbled him so much, that he scarce swore another oath aloud during the whole journey."

The 1842 poem, "The Ingoldsby Legends" also uses this figure of speech. In this poem, a Frenchman examines a watch and says, "Superbe! Magnifique!" (with his tongue in his cheek).

The modern-day ironic meaning is originated from the idea of controlled laughter by biting one's tongue to suppress one's laughter.
Tongue-In-Cheek Examples
Example 1:

Imagine that Armin planned a surprise birthday party for Jordan. He spent all day cleaning the house, making food, and decorating it. When she arrives, she looks around with a frustrated face and says, "Didn't you have time to clean the house?, This is the best you could do?." While Armin looked concerned and sad, she starts laughing and hugged him by saying, "It looks beautiful!."

The sentence - Didn't you have time to clean the house?, This is the best you could do? was said tongue-in-cheek.

Example 2:

"Was she speaking with tongue-in-cheek when she said Amanda should be the cheerleader captain?"

This was the meaning of the idiom tongue-in-cheek, although it has light humor and meaning ascertained, care should be taken to not offend anyone's feelings or sentiments.

Tongue-in-cheek jokes can be facetious or they can be ironic. The facial expression or body language of the speaker is generally not playful with a little bit of indication that he/she is just being humorous. Comedy, horror, and teen movies are examples wherein the director tries to represent somebody in a humorous way using this element.