Idiom medium 45 / 51
“tongue in cheek”
i · The common misuse One wrong form
ii · What it meansTwo lines, no filler
The gesture is literally putting your tongue against the inside of your cheek — a historical sign of ironic or sarcastic delivery. 'Tongue and cheek' is a mishearing.
iii · Memory hookKeep this one
Tongue IN cheek — the tongue goes inside, it's one gesture. 'And' would list two body parts.