Theophilus Abbott was an American Magical Historian who identified families of “Scourers,” witches and wizards who persecuted their own kind and also innocent No-Maj Muggles by selling them out during the Salem Witch Trials and other situations (MNA).
Historian and Writer
The name Abbott may be intended to connect this person to the Abbott family in England, a family which included Hannah Abbott in Harry's year at Hogwarts.
There was an American scholar with a similar name: Theophilus C. Abbot (one less "t" on the last name). He lived from 1826-1892 and taught English in Vermont and Ann Arbor, Michigan.