When the papacy left Rome for Avignon in 1309 AD the church entered a mode of money making. This was accomplished by selling almost every office it could as well as indulgences. One of the other things that could be purchased was legitimacy for illegitimate children. In 1342-1343 there were 614 grants of legitimacy and of those 484 were for members of the clergy.

(Book – A Distant Mirror: The Calamitous 14th Century – Barbara W. Tuchman)