Originally there was a "Bach Society". In her constitution it's goal was to organize the whole work of Johann Sebastian Bach, which in the very beginning only existed very unorganized and confusing. That lead to the creation of the BWV, which in German is the "Bach Werke Verzeichnis", which in English is The Bach Work Index. According to it's statute the society dissolved with having reached this goal.
And that is the reason, the nowadays follow-up society, which is again now around for another one hundred and ten years, is called the "New Bach Society", the Neue Bach Gesellschaft.
99 Music Calendars, Composers Calendars and Bach Calendars