Of Old Norse origin, from ei ‘ever, always’ (or einn ‘one, alone’) + ríkr ‘ruler’ (see Eirik). It was introduced into Britain by Scandinavian settlers before the Norman Conquest. As a modern given name, it was revived in the mid 19th century and has remained in use since.
English and Scottish: patronymic from the medieval personal name Nel or Neal, Anglo-Scandinavian forms of the Gaelic name Niall (see Neill). This was adopted by the Scandinavians in the form Njal and was introduced into northern England and East Anglia by them, rather than being taken directly from Gaelic.