N. nâr n. “rat” (Category: Mouse, Rodent)
A noun in The Etymologies of the 1930s glossed “rat” derived from primitive ᴹ✶nyadrō under the root ᴹ√NYAD “gnaw” (Ety/NYAD). Tolkien gave the intermediate form naðr, but it is not clear why the ð vanished; compare N. nadhor “pasture” < ᴹ√NAD (< *nadrō?), and indeed Tolkien had a variant archaic form naðor “rat” which shows the normal phonetic developments (EtyAC/NYAD).
Reference ✧ Ety/NYAD ✧ “rat”
|ON. naðr > nâr||[naðr] ? [nâr]||✧ Ety/NYAD|