In the second part of _The Book of Lost Tales_ (p. 288) it is said that
Tavrobel, the city of elves, is situated near the conjunction of two
rivers, _Gruir_ and _Afros_. I'm very interested in any
suggestions about a possible etymology of these names!
Thanks in advance!
[Christopher Tolkien notes (I:196, V:413) the apparent correspondence of the rivers _Gruir_ and _Afros_ with the Trent and the Sow, in conjunction with the identification of _Tavrobel_ with the village of Great Haywood in Staffordshire. Ekwall tells us (_Oxford Dictionary of English Place-Names_) that "Trent" derives utlimately from British (Celtic) _Trisant�n_ < _tri-_ 'through, across' + _sant�n_ *'road': i.e., cross-roads, ford. "Sow", meanwhile, is cognate with Gaulish (Celtic) _Savus_ < *_seu-_ 'to flow, liquid', whence Old English _s�aw_ and Welsh _sug_ 'juice', Old Irish _suth_ 'milk'.
With Trent 'ford, cross-roads' in mind, it is interesting to compare Gnomish _Afros_ with the "Gnomish Lexicon" entry _adros_ 'a crossing, ford' (which replaced earlier _athrod_ of the same meaning). On the other hand, GL also has _av(r)os_ 'fortune, wealth, prosperity' (an alteration from earlier _avos_), which is closer in form to _Afros_.
If _Afros_ is indeed to be identified with the Trent, this leaves _Gruir_ as the Sow. The closest forms in GL are _grum_, _gruim_ 'fierce', _grui_ 'ferocity, horror'. However, from what I can glean from various web-sites, the Sow is in fact a narrow (max. width of 3 meters) and often shallow river: not exactly fierce-sounding. On the other hand, the Trent is one of only two bore rivers in England: that is, it has tidal bore waves that flow up-river. CFH]