- Ilkorin: môr ("night")
The element mor appears in a large number of compounds. Christopher Tolkien notes in the Etymologies that the entry MOR- is "extremely confused through changes and afterthought additions" and that it is not clear if "all the forms given were intended to stand". It can therefore be hard to know if the element mor in a compound is supposed to consist of a certain derivative of MOR.
Based on manuscripts held at the Cushing Memorial Library and Archives collection, Madeline J. Keyser has suggested that Tolkien was inspired by a real-world word mora, which "seems to be of North (Scandinavian) and West Germanic origin — the Latin root is found in Modern English words such as murky, and in other Germanic words associated with darkness". A manuscript note appears to consist of the glosses mora "dark", moranya "darker", and moranta "darkest".
- J.R.R. Tolkien; Humphrey Carpenter, Christopher Tolkien (eds.), The Letters of J.R.R. Tolkien, Letter 297, (dated August 1967) (root appearing as "√MOR")
- J.R.R. Tolkien, "Words, Phrases and Passages in Various Tongues in The Lord of the Rings", in Parma Eldalamberon XVII (edited by Christopher Gilson), pp. 73, 81 , 165 (root appearing as "√MOR-")
- J.R.R. Tolkien, Christopher Tolkien (ed.), The Silmarillion, "Appendix: Elements in Quenya and Sindarin Names" (element appearing as "mor", signifying "dark")
- J.R.R. Tolkien, Christopher Tolkien (ed.), The Lost Road and Other Writings, Part Three: "The Etymologies", pp. 373-4
- J.R.R. Tolkien, "Addenda and Corrigenda to the Etymologies — Part One" (edited by Carl F. Hostetter and Patrick H. Wynne), in Vinyar Tengwar, Number 45, November 2003, p. 35
- Madeline J. Keyser, "Sixteen Philological Books and Notes from the Library of J.R.R. Tolkien" dated 30 December 2012, Tolkien Library (accessed 3 January 2013)