Originally a variant of Helen, although now no longer associated with that name. Initial H- tended to be added and dropped rather capriciously, leading to many doublets (compare for example Esther and Hester). It is also sometimes used as a short form of Eleanor, to which, however, it is unrelated.
North German: from a Germanic personal name composed of the elements ēo ‘law’, ‘custom’, ‘right’ (a rare element in personal names, found mostly in Old Saxon) + wald ‘rule’. This name was borne in the 7th century by two brothers (distinguished as ‘Ewald the White’ and ‘Ewald the Black’) who were missionaries in North Germany. They became the patron saints of Cologne and Westphalia, and so contributed to the popularity of the personal name (and hence the eventual frequency of the surname) in these areas.