Pettanko refers to a type of anime characters who are women, possessing small breasts and are obsessed with this trait in themselves, either in a negative or a positive way.
The difference between a regular flat-chested anime character and a “pettanko” is in the fact that the latter is either extremely ashamed, insecure or on the other side, extremely proud about their moderately developed assets.
Another way of referring to a “pettanko” character is “Delicious Flat Chest” or DFC for short.
The term got adopted into English during the surge of otaku culture in the late decades of the 20th century.
There are several examples of overly self-conscious characters in manga and anime series, so it is consequential, that those frequently indulging in the said art forms, had adopted the phrase to refer to these people.
The rise in popularity of hentai in the 2000’s had also led to a grown interest in “pettankos” although they are often mistaken for underage girls or lolis, because they look underdeveloped because of their flat chest.
An entry was uploaded on the subject to Urban Dictionary in 2009.