Bonenkai (忘年会 in Japanese Kanji) is a Japanese drinking party, which is held among co-workers’ groups or friends at the end of the year (on December).
忘 (“bou”) = to forget
年 (“nen”) = year
会 (“kai”) = gathering
As its name implies, the purpose of this party is to forget all of the troubles of the past year, and to look to the New Year and the new future ahead of them with hopes.
A bōnenkai does not take place on any specific day, but they are usually held in December.
The tradition started in the 15th century during the Muromachi period as gatherings to express thanks. At that time, the parties were known as noukai (great achievement gathering). By the 18th century, they had become known as bōnenkai, or year-end parties.
Bōnenkai are seen as times for bureiko or letting one’s hair down and not worrying about the boss/employee formal relationship or the rank and age divisions.