and Ghibellines. Two great parties whose conflicts make up the history of Italy and Germany in the twelfth, thirteenth, and fourteenth centuries. Guelph is the Italian form of Welfe, and Ghibelline of Waiblingen, and the origin of these two words is this: At the battle of Weinsburg, in Suabia (1140), Conrad, Duke of Franconia, rallied his followers with the war-cry Hie Waiblingen (his family estate), while Henry the Lion, Duke of Saxony, used the cry of Hie Welfë (the family name). The Ghibellines supported in Italy the side of the German emperors; the Guelphs opposed it, and supported the cause of the Pope.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Guelphs from Infoplease: