An adjective meaning “sad, gloomy” from the primitive form ᴹ✶dimbā (Ety/DEM). A related form dimb “sad” appears as an element in the Ilkorin name Dimbar. This form dimb is likely either a stem form or a more primitive form.

Possible Etymology: There is no language marker for the word dem in The Etymologies (Ety/DEM). David Salo (GS/248) and Didier Willis (HSD/dem) both suggested that it is Noldorin, based on (1) the fact that the element dimb is explicitly marked as an Ilkorin word for “sad” and (2) the phonological evidence, in that primitive ᴹ✶dimbā would develop into Noldorin dem.

However, the key phonological changes producing dem from primitive ✶dimbā also occurred in Ilkorin: short [i], [u] became [e], [o] preceding final [a] and final [mb] became [m]. I believe that dem is in fact an Ilkorin word, and that the element Ilk. dimb “sad” appearing earlier in the entry is a stem form, as noted above.

Conceptual Development: The root form of this word in The Etymologies was first written ᴹ√DIM, rejected and replaced by ᴹ√DEM (EtyAC/DEM). As pointed out by Helge Fauskanger, the primitive forms could only be derived from the root ᴹ√DIM (AL-Ilkorin/dem), so it seems that Tolkien reverted the change of ᴹ√DIM >> ᴹ√DEM. An earlier form demb “gloomy, sad” of this adjective (EtyAC/DEM) likely reflects this vacillation.