William is among the most commonly found Medieval given names, and as a result, is among the most common surnames. Williams is a patronymic form.
William is derived from an Old French given name with Germanic elements wil = desire, will + helm = helmet, protection.
introduced by followers of William the Conqueror and became in short
order one of the most popular given names in
Surnames based on the Christian name of the father are very common in English-speaking countries. Either the name is obvious (John William) or an "s" might be added, giving names like Williams.