Melko masc. name "Mighty One", name of the rebellious Vala, usually called Melkor (MIL-IK, MOR; FS MR:350 confirms that the form Melko_ is still valid in Tolkien's later Quenya, though not interpreted "Greedy One" as in the Etymologies)_
melkormasculine name. He who arises in Might, (lit.) Mighty Arising
Name of the Valar whose rebellion brought evil into the world (S/16), more commonly known as Morgoth. His name is an ancient compound of the root ✶(m)belek- “mighty” and ✶ōre “rising”, so meaning: “Mighty Arising” (MR/350, PE17/115), translated more loosely as “He who arises in Might” (WJ/402, PM/358). This name also appeared in the longer form Melkórë (MR/350, PE17/115). This is one of the names Tolkien generally spelled with a “k” (like Kementári and Tulkas) despite normally representing the [k]-sound with “c” in Elvish, though in a few places he did write Melcor (MR/362, VT49/24).
Possible Etymology: In the name Melkorohíni “Children of Melkor” (MR/416), the stem form for Melkor seems to be Melkoro-. This is consistent with the primitive form ✶Mbelekōro appearing in the “Quendi and Eldar” essay from 1959-60 (WJ/402). Elsewhere its primitive form was given as ✶Mbelekōre (PE17/115) and its ablative form appears in notes from the mid-1960s as Melkorello (VT49/6-7), indicating a stem-form of Melkore-, consistent with the long form Melkórë noted above.
Conceptual Development: This name first appeared in the earliest Lost Tales as ᴱQ. Melko without its final -r (LT1/47). This name appeared in the Qenya Lexicon glossed “God of Evil” but without an etymology (QL/60). In the contemporaneous Gnomish Lexicon, it was connected to the root ᴱ√melek/mbelek/belek, along with ᴱQ. velka “flame” (GL/22). It is likely that Tolkien first considered this name as representative of his “fiery” evil, as his contemporaneous (but later abandoned) name ᴱQ. Yelur was that of “wintery” evil.
In some texts from the 1920s, ᴱQ. Melko was given as the derivative of (unglossed) ᴱ✶Mailiko (PE13/149; PE14/69), and the name ᴹQ. Melko appeared in The Etymologies from the 1930s as a derivative of ᴹ✶Mailikō < ᴹ√MIL(IK) “greed, lust” (Ety/MIL-IK). The form Melkor (with an -r) appeared towards the end of Silmarillion drafts from the 1930s (LR/332). This was the form used thereafter, starting with Silmarillion revisions from the 1950s-60s (MR/7, MR/22 note #5).