His name is the Old Norse equivalent of the goddess Nerthus? described by Tacitus. It has been suggested by [H.R. Ellis Davidson]? in [Gods and Myths of Northern Europe]? that there was possibly originally a male and female pair of deities, Niord and Nerthus, with Freyr later replacing Nerthus. Davidson also makes the point that there were other male/female pairings of Norse gods of whom little is known but their names, e.g. Ullr? and Ullin?.
An alternative spelling of Niord is Njord.