An unknown bishop who was the source of the Est! Est! Est wine legend. As John Evelyn describes it:
After seven miles’ riding, passing through a wood heretofore sacred to Juno, we came to Montefiascone, the head of the Falisci, a famous people in old time, and heretofore Falernum, as renowned for its excellent wine, as now for the story of the Dutch Bishop, who lies buried in St. Flavian’s church with this epitaph:
“Propter Est, Est, dominus meus mortuus est.” ((Latin: “Because of (IT) IS, my lordis dead.”.
Because, having ordered his servant to ride before, and inquire where the best wine was, and there write Est, the man found some so good that he wrote Est, Est, upon the vessels, and the Bishop drinking too much of it, died.
It is not certain exactly who this bishop was – this article on the bishop has a few good theories.
Wikipedia for background, portrait.