Wikipedia
Akanbe
, also spelt , is a Japanese facial gesture indicating crazy mockery, also known in France as mon œil. It consists of someone pulling down one's lower eyelid to expose the red underside towards someone, often accompanied by the person sticking their tongue out. It is considered an immature taunting gesture.
The use of the term was first mentioned by early 20th century author Katai Tayama, in his 1909 story , as a gesture used by the male students in the story. In the story, it gives the etymology as a corruption of .
The gesture is used often in manga and anime by tsundere characters.