Traditionally (since Sethe 1911) derived from n(j)(“of, belonging”) + swt(“sedge”) in a direct genitive construction with n(j) used as a noun, literally ‘the belonging one of the sedge’, i.e. ‘the one to whom Upper Egypt belongs’, the sedge being an emblem of Upper Egypt. The odd glyph order in the written form is probably due to a preference for forming compact groups of hieroglyphs.
However, this interpretation has been challenged, as Helck, Schenkel, and others have argued that the plant represented by swt is not the emblem of Upper Egypt at all; Schenkel also suggests the reconstructed vocalization of the word does not support such an etymology. Peust goes so far as to say the word has no special connection with Upper Egypt, and derives it as borrowed from Sumerian𒉺𒋼𒋛(ensi2) with the Egyptian noun-forming suffix -w.
Much debate centers around the apparent variant form nzw, attested from very early times, and its relation to nswt. Some authors see it as a dialectal variant of the latter; others treat it as an entirely separate word. Schenkel instead reads nswt in a different order as ntsw and considers it a variant spelling of nzw, hypothesizing that the Egyptian z is an affricate equivalent to ts; a number of authors have adopted this suggestion.
In some outdated publications, nswt was read as stn, stnj, or swtn, but these readings are now generally rejected.
Sometimes, based on the traditional etymology, a fuller reading as njswt or nj-swt is given.