kieli poskessa

HIM
2.1.2014

tarkoittaa leikkimielellä, ei vakavasti otattevaksi. Sanonta on käännöslaina englannin kielen ilmaisusta tongue in cheek.

Osoitteesta http://kidshealth.org/kid/talk/come_from/tongue_cheek.html
löytyy tällainen selitys:

Tongue-in-Cheek
This funny-sounding expression indicates that someone just told a joke or isn't being serious! If someone says something "tongue-in-cheek," they're usually kidding.
It's believed that this saying was created by an English humorist in the 1800s. Most people have difficulty saying anything with their tongue in their cheek. But some people actually do stick their tongue against the inside of their cheek after saying a joke to show that they're only kidding.