A Doriathrin noun for “mountain” derived from the root ᴹ√ÓROT (Ety/ÓROT). Its Old Noldorin cognate ON. oroto suggests a primitive form *✶orotō, where the second [o] was lost due to the Ilkorin syncope [orto]. Later the [t] became [θ] (“th”) because voiceless stops became spirants after liquids and voiceless stops in Ilkorin. Both these developments were noted by Helge Fauskanger (AL-Doriathrin/orth). This word has two distinct plural forms attested: Dor. orthin (Ety/ÓROT) and Ilk. urthin (EtyAC/WATH); this could represent distinct rules for the formation of plural-nouns in the two dialects.