This root and similar ones were used for “strife” or “hatred” over Tolkien’s lifetime, but the exact forms varied considerably. One of its more notable derivatives was Q. ohta “war” which Tolkien introduced in the Early Qenya Grammar of the 1920s (PE14/45). However, the earliest precursor of this root was ᴱ√KOSO “strive” from the Qenya Lexicon of the 1910s, but its Gnomish form goth is more representative of its actual primitive form GOÞO (QL/48). At this early stage its most notable derivative was G. Gothmog/ᴱQ. Kosomoko or Kosmot “Strife-and-hatred” (PME/48; LT2/216), but in later writings N. Gothmog was given a new etymology as a combination of ᴹ√GOS “dread” and ᴹ√MBAW “oppress” (Ety/GOS, MBAW).
In The Etymologies of the 1930s the root became ᴹ√KOT “strive, quarrel”, soon revised to ᴹ√KOTH, with derivatives in both Quenya and Noldorin (Ety/KOT). One important new derivative of this root was N. Morgoth “Black Foe”, the first time this name was given a clear etymology, though the name G. Morgoth itself dates back to the earliest Lost Tales (LT2/67). In the first version of the Tengwesta Qenderinwa (TQ1), also written in the 1930s, Tolkien gave ᴹ√KHOT “be wroth, quarrel” as the basis for ᴹQ. ohta “war” (PE18/62). The root form √KHOT also appeared in the second version of the Tengwesta Qenderinwa (TQ2) written around 1950, in one place as revision of a deleted form √KOT; the gloss likewise was changed from “be wroth, quarrel” to “hate” (PE18/85 note #72, PE18/87 and note #77).
In the Outline of Phonology (OP2), Tolkien described a new etymology for the name of Morgoth, basing it on ancient ✶Moriñgotho “Black Foe” = ✶mori + ✶ñgothō; in “modern” Quenya this came to be Q. Morños/t [þ], pronounced morgos/t (PE19/81). Although Tolkien began composing OP1 in the early 1950s, this particular section was a revision written in red ink and thus was later, and it had some additional changes in green ink which Tolkien used to revise OP2 in 1970 (PE19/81 note #65). As Christopher Gilson suggested, the new etymology was certainly connected to the following passage in the later drafts of the Silmarillion:
> Then suddenly Feanor rose, and lifting up his hand before Manwë he cursed Melkor, naming him Morgoth, the Black Foe of the world. [In an author’s footnote] By that name only was he known to the Eldar ever after. (In the ancient form used by Feanor it was Moriñgotho.) (MR/295).
This new etymology might reflect a change of this root to ✱√ÑGOT(H), but it seems Tolkien was not fully committed to this change in the 1950s and 60s. In the Ambidexters Sentence from 1969 Tolkien switched Q. Moringotto to Morikotto before settling on Melkor (VT49/6). There is also the name S. Thuringud “Hidden Foe” from late Silmarillion drafts (WJ/256) whose final element -gud “foe” may well be derived from √KOT (✱kōt(e)) as suggested by Patrick Wynne (VT49/25). Thus Tolkien seems to have vacillated on the exact form of this root frequently over his lifetime.
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is best to assume this root is √KOT, as this preserves the largest number of attested words as Tolkien wrote them, the only major exception being Moringotto. Likewise, I believe the ancient sense “strife, quarrel” is more compatible with attested words than “hate”.
This root and its variants meant something like “gather” for much of Tolkien’s life. The earliest form of this root was given as ᴱ√HOSO in the Qenya Lexicon of the 1910s with variant form XOÞ-, the latter more representative of its true form (IPA [xoθ-]) given its Gnomish form hoth (QL/41). This early form was unglossed but had derivatives like ᴱQ. hos (host-) “folk, people, tribe”, G. hoth “folk, people, †army” and G. hosta- “gather, collect” (QL/41; GL/49). This early root was confused with ᴱ√OSO “through loss of ·h· in cpds”, another unglossed root but probably meaning something like “✱enclosure” (QL/41, 71).
The verb form ᴱQ. hosta- “gather” appeared in the Early Qenya Grammar of the 1920s (PE14/33-34), and the root ᴹ√KHOTH “gather” appeared in The Etymologies of the 1930s with derivatives similar to its earlier iteration: ᴹQ. hosto “crowd, assembly”, N. hoth “host, crowd” and ᴹQ. hosta- “to collect” (Ety/KHOTH). The root √KHOT “gather, together in confusion, jumble” appeared in etymological notes from the late 1950s or early 1960s where it was the basis for S. hoth “host” and Q. hosta- “gather hastily together, pile up” (PE17/39). The Quenya verb reappeared with the gloss “gather” in the Markirya poem from the late 1960s (MC/222), indicating the continued validity of the root. The various derivatives of the root could be from either √KHOT or √KHOTH, so the actual primitive form is mostly academic.