A Doriathrin noun for “fog” written hiðum in The Etymologies, and derived from the primitive form ᴹ✶khithme [kʰitʰme] (Ety/KHIS, EtyAC/KHIS). This word illustrates several interesting phonetic changes in Ilkorin.

1. Both the aspirates became voiceless spirants: [kʰ-] > [x-] and [-tʰ-] > [-θ-].
   1. Later the initial [x-] became [h-].
   2. Meanwhile the medial [-θ-] voiced to [-ð-] (“dh”).
2. The primitive final [e] was lost.
3. Afterwards, the resulting final [m] became syllabic and developed into [-um].