A Doriathrin noun for “sorcery” (Ety/ÑGOL). The elements of this word seem to be a combination of derivatives of the roots ᴹ√DOƷ and ᴹ√ÑGOL. If it were derived from such a primitive form, it would imply that in its phonological history the [o] because [u] in both syllables. This does not seem to be a general rule in Ilkorin, however: compare Ilk. dorn and (n)golo. A simpler explanation would be that it was a loan word from Noldorin: N. durgul seen in a marginal note (EtyAC/ÑGOL).
Conceptual Development: There is a rejected form dûghol in this entry of The Etymologies that may represent Tolkien’s first attempt to formulate a native Ilkorin word for “sorcery” (EtyAC/ÑGOL). Similar forms appear among the precursors to S. Dol Guldur in Lord of the Rings drafts from the 1940s: Dol Dúgol or Dol Dúghol (TI/178; WR/122). The entry also has a deleted variant form of gûl of Ilk. (n)gôl, so it may be Tolkien originally envisioned a different phonological history of [o] in Ilkorin allowing the production of words like durgul. Perhaps he added the Noldorin form durgul in the margin because he abandoned [o] > [u] in Ilkorin.