AttestedNido in iter 12 of the Antonine Itinerary

WhereNidum is generally assumed to be the Roman fort inside the modern town of Neath, at SS74749773, a little way up the river Neath from the coast.  However, to fit the Itinerary's mileages a better guess might be the marching camp at Blaen-cwm-Bach at SS79709878 more into the hills.

Name origin:  Neath may just mean ‘low-down’, because the river and its parallel in Yorkshire, the Nidd, both pass through noticeably deep, long valleys in their upper reaches, as does the Neda in Greece.  This simple explanation has not caught on because the excellent parallels in English (such as nether and beneath) and in other language families have no good equivalent in Celtic.  The deeper root is PIE *ni- ‘down’, itself built upon *en- ‘in’.  Evidence for *ni- is strong in Indo-Iranian languages or as relatives in Basque.  Alternatives, such as the ‘shining’ idea of Ekwall (1928), are unattractive.  Welsh nyth ‘nest’ from Latin nidus, plus conceivably Greek νηδυς ‘womb, belly’, derive from *nizdos ‘sit-down place’.

Notes: At least eleven more rivers across Europe were originally named *Nida, *Neida, or *Neda (Krahe 1963), including possibly the Nith through Dumfries.  They are usually explained as derived from PIE *neid- ‘to flow’, hence Sanskrit nidati and see Diefenbach (1851:104) for other possible cognates, such as Greek νιζω ‘to wash’, English neat, French nettoyer ‘to clean’, etc.  Delamarre (2003:234-5) likens *nitio- to Sanskrit nitya ‘indigenous’.  The river Nene, flowing through low ground into the Wash has no certain etymology, but has been suggested to come from PIE *neigw- ‘to wash’, whose descendants include Germanic nix (water sprite), Irish nigid ‘washes’, and Sanskrit nenekti ‘to wash clean’.

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