Further Research: Caitlin Christiana Wintour

Cistercian Office of the Dead
"The almost-daily Office of the Dead seems to have been instituted by St. Anglebert in 800-801 and was known by the Synod of Aachen. It was widely used in monasteries including those in the Cluniac tradition. In a period of uncertainty about salvation, coinciding with the evolution of a doctrine of purgatory, the Office of the Dead was not discontinued by the Cistercians. No doubt the perpetual offering of substantial suffrages for the dead was a very attractive proposition to potential benefactors who, being rich, probably recognised the necessity of some life insurance."

Exordium, Unit 9 -- from the Cistercian Order of the Strict Trappists