Guelph (n.)

also Guelf, one of the two great parties in medieval Italian politics, characterized by support of the popes against the emperors (opposed to the Ghibellines), 1570s, from Italian Guelfo, from Old High German Welf, name of a princely family that became the ducal house of Brunswick, literally "whelp," originally the name of the founder (Welf I). The family are the ancestors of the present dynasty of Great Britain. The name is said to have been used as a war-cry at the Battle of Weinsberg (1140) by partisans of Henry the Lion, duke of Bavaria, who was of the family, against Emperor Conrad III; hence it was adopted in Italy as the name of the anti-imperial party in the Middle Ages.