Geoffrey IV, also called GEOFFREY PLANTAGENET, byname GEOFFREY THE FAIR, French GEOFFROI PLANTAGENET, or GEOFFROI le BEL (b. Aug. 24, 1113--d. Sept. 7, 1151, Le Mans, Maine [France]), count of Anjou (1131-51), Maine, and Touraine and ancestor of the Plantagenet kings of England through his marriage, in June 1128, to Matilda (q.v.), daughter of Henry I of England. On Henry's death (1135), Geoffrey claimed the duchy of Normandy; he finally conquered it in 1144 and ruled there as duke until he gave it to his son Henry (later King Henry II of England) in 1150.
Geoffrey was popular with the Normans, but he had to suppress a rebellion of malcontent Angevin nobles. After a short war with Louis VII of France, Geoffrey signed a treaty (August 1151) by which he surrendered the whole of Norman Vexin (the border area between Normandy and Œle-de-France) to Louis. [Encyclopaedia Britannica CD '97]
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The Plantagenet family name was originally just a nickname for Geoffrey. He many times wore a sprig with yellow flowers in his hat. The flower was named "genet" or "genistae" in the French of the times--thus his nickname was "Plant-a-Genet". Genet was supposedly a traditional flower of the Anjou family dating back to the time of Fulk, The Great, Count of Anjou 898-941 who was scourged (in order to atone for past sins) with broom twigs of the Genet while on pilgrimage in Jerusalem. Most people of the times had personal nicknames such as "Beauclerc", "Curtmantel", "Longshanks", and "Lackland", but Geoffrey's stuck and eventually (many generations later) became the family name. Geoffrey's immediate descendants were probably not known as the Plantagenet family at the time they lived, it was only later that the Plantagenet family name was applied to all descendants of Geoffrey.