While some scholars have disputed various aspects of the Nerthus cult, from her name to her status as a genuine Germanic earth goddess, none of these arguments has proven particularly effective in light of a comprehensive examination of the evidence. Most often doubted is the name Nerthus itself. Tacitus writes, Nerthum, id est Terram matrem, “Nerthus, that is, Mother Earth.” Nerthus is only one of three divine names of ethnic origin in Germania, demonstrating that Tacitus probably had a Germanic source for it.
Some scholars have disputed the certainty of this reading because of variant forms of the name found in the manuscripts, all of which date from the fifteenth century or later. These variant readings are: Nerthum, Nertum, Neithum, Nehertum, Necthum, Herthum, and Verthum.Jacob Grimm addressed this point as early as 1835. Rather than any nationalistic desire to connect German folklore to Old Norse mythology, as some have suggested, the authority behind Grimm’s Law relied on his skills as a linguist, clearly stating that “the manuscripts collated have this reading.” Nor was this his preference: “I should prefer Nertus to Nerthus, because no other German words in Tacitus have TH, except Gothini and Vuithones.” He rejects the reading Herthus, “though the aspirate in herda might seem to plead for it, the termination –us is against it.” Thus, the assertion by Lotte Motz that Grimm selected the name “because it coincides phonetically with Njörðr” is without foundation.. Grimm, Teutonic Mythology, p. 251. Lotte Motz, The King, The Champion and the Sorcerer (1996), pg. 116. Emphasis by Motz..Regarding the reading of the name of the goddess in Germania chapter 40, whom scholars commonly refer to as Nerthus. John McKinnell, (Meeting the Other in Old Norse Myth and Legend, p. 52) explains the correctness of this reading:.“The usually accepted stemma has three families, and readings shared by the best manuscripts of any two of them are thought likely to be correct. The best X group manuscripts (Vatican, Cod. Vat. 1862, Leiden UL XVIII Periz.Q.21) read Neithum; the best y manuscripts (Cod. Vat. 1518, Codex Neapolitanus) have Nerthum, and the best Z manuscript (Iesi, Æsinas Lat. 8) reads Nertum. The sound /th/ did not exist in classical Latin, though the spelling is found in words derived from Greek or the Germanic languages (such as thesaurus 'treasure', or the name Theodoricus). Tacitus would therefore be unlikely to introduce the spelling th gratuitously. In the fifteenth century, the Italian scribes who produced most of the earliest surviving manuscripts (including the Iesi manuscript) would have a natural tendency to replace it with , as was consistently done in their native language (see Italian tesoro, Teodorico), but would be very unlikely to do the reverse. Nerthum is therefore more probably correct than Nertum. If both Y and Z should read Nerthum, that reading must be preferred. A different stemma, proposed by Robinson, has only two groups, and the best manuscripts in both read Nerthum. Whichever stemma is correct, Nerthum therefore seems the likeliest reading, although it could represent either a grammatically masculine Nerthus or a grammatically neuter Nerthum.”
Nerthus is most often identified as one of the Vanir. It has long been recognized that the name Nerthus is an etymon of Njörðr, the most senior of the named Vanir gods, and father of Freyr and Freyja. Grimm himself noted that the name Nerthus was identical to the later Old Norse name Njörðr, an “identity as obvious as that of Freyr to Freyja,” [TM ch. 10]. According to John McKinnell (2005), the development would be “Nerthus > *Njarðuz (breaking) > *Njörðuz (u-mutation) > Njörðr (synscope).” Much has been made of this apparent gender gap..The form Hertha is a false reading of comparatively modern origin. In 1519, Rhenanus, the pious scholar who published Tacitus, wrote Herthum for Nerthum, manifestly the same as the Old High German Herda, earth. Based on his authority, the text of Tacitus was uniformly given as Herthum up until 1817, when editors such as Franz Passow restored Nerthum to the Latin text.. Gentleman’s Magazine (Feb. 1856), p. 143 in “Heligoland” by William Bell: "Not less discussion than the situation of the island has the name of its presiding deity given rise to. Up to the year 1817 the text of Tacitus was uniformly given Herthum id est Terram matrem colunt and the masculine ending in -um was not only not inconsistent with female Teutonic names but a proof of high antiquity as we find it in the names of Hendus and Gudrun the latter the name of a female giving title to an ancient poem which Gervius has called the German Odyssey as the Niebelungen has been designated the German Iliad. But in that year Passow proposed to restore for Herthum, Nerthum as in the earliest printed copies in which he was borne out by a formidable array of MSS designated as Cod Hummel et Longol. Spir. Pal. Mon. Vienn."
Odin's Wife (2018) by William P. Reaves