A verb for “die” in Early Noldorin Grammar of the 1920s with present form gwardh indicating vowel gradation (PE13/132), so that it was likely based on the early root ᴱ√GWṚÐṚ (QL/104) with a/u variations due to the different developments of long syllabic ṝ vs short ṛ.
Conceptual Development: The verb G. gor-“die” appeared in the Gnomish Lexicon of the 1910s related to gurthu “death” (GL/41, 43), thus also based on the early root ᴱ√GWṚÐṚ (QL/104).
Neo-Sindarin: S. gurth “death” survived in Tolkien’s later writings, so in theory the Gnomish verb gor- could be salvaged as a derivative of the later root √ÑGUR “die”. However, gor- already serves various functions in Sindarin, so I’d stick with the later verbs fir- and [N.] gwanna- for “to die”.
This word appeared as gwath {“field” >>} “bark” in Early Noldorin Grammar of the 1920s (PE13/120). This form also appeared in Noldorin Word-lists of the 1920s, but it was deleted and replaced by gwadh “bark, skin, peel” as a derivative of ᴱ✶(s)wada (PE13/146).