A noun glossed “shade” (shadow) derived from the root ᴹ√WATH (Ety/WATH). It is a clear example of how [[ilk|initial [w] became [gw]]] in Ilkorin, and it appears in several names: Thuringwethil “(Woman of) Secret Shadow” and Urthin Gwethion (unglossed but presumably “✱Mountains of Shadow”).
Doriathrin
-ath
noun. collective plural
gwath
noun. shade
A class plural suffix, identical to N. -ath (PE21/57). It is possible this suffix was also used as (and was perhaps inspired by) the Gnomish general plural suffix -th.