During the twelfth century, belief in undead vampires flourished in many parts of England. We know of this from the writings of three chroniclers who lived at the time: William of Newburgh (1136 – c.a. 1200), William of Malmesbury (d. ca. 143), and Walter Map (d. ca. 1208). The belief at the time was that a corpse which left its grave at night to trouble the living was possessed and animated by a demon. This was usually the corpse of a person who had lived a sinfull life.
One the most interesting of these accounts is one of several reported by William of Newburgh. The revenant in this case was that of a knight who had served the lord of Ainswick Castle in Yorkshire . The knight had led a lewd, wicked life. He died as the result of falling from his roof while spying his own wife engaged in adultery. After his burial, he was seen again, prowling through the streets and around the houses in his village. His flesh was rotting and a plague resulted from the fetid air emitted.
The villagers finally destroyed this creature by exhuming the corpse and cremating it. They found the corpse to be ruddy and swollen. They attributed this condition to being due to the corpse being bloated with the blood that it had drank from his victims. The people then dragged the corpse to a place outside their village and cremated it. After that, both the appearances of the vampire and the plague ended. In this account, William of Newburgh applies the Latin name sanguisuga, which literary means “blood sucker”, to the revenant.
From The Vampire in Europe by Montague Summers