William Thurman

(male) Probably the most successful of all the Old French names of Germanic origin that were introduced to England by the Normans. It is derived from Germanic wil ‘will, desire’ + helm ‘helmet, protection’. The fact that it was borne by the Conqueror himself does not seem to have inhibited its favour with the ‘conquered’ population: in the first century after the Conquest it was the commonest male name of all, and not only among the Normans. In the later Middle Ages it was overtaken by John, but continued to run second to that name until the 20th century, when the picture became more fragmented.

English (East Midlands): from the Middle English personal name Thurmond, Old Norse þormundr, composed of the elements þórr, name of the Norse god of thunder (see Thor) + mundr ‘protection’. Reaney and Wilson suggest that, Thurmond having been an uncommon personal name, this surname may also represent the commoner name Thurmod, Thormod with the second element derived from Old Norse móþr ‘mind’, ‘courage’, but assimilated to -mund (a common second element in other compound names).