Old French name of Germanic (Frankish) origin, derived from gisil ‘pledge’ + berht ‘bright, famous’. It was adopted by the Normans and introduced by them to Britain. This was the name of the founder of the only native British religious order (abolished at the Dissolution of the Monasteries), St Gilbert of Sempringham (?1083–1189), in whose honour it is still sometimes bestowed, especially among Roman Catholics. It gained a wider currency in the 19th century.
Scottish, English, North German, French, and Catalan: from a Germanic personal name composed of the elements hrōd ‘renown’ + gār, gēr ‘spear’, ‘lance’, which was introduced into England by the Normans in the form Rog(i)er. The cognate Old Norse Hróðgeirr was a reinforcing influence in Normandy.