Tolkien used a number of similar roots for “bay” but their exact form varied over his life. The earliest form was ᴱ√KOPO “keep, guard?” (the question mark is Tolkien’s) from the Qenya Lexicon of the 1910s with the derivative ᴱQ. kópa “harbour” (QL/47). This root and its Qenya derivative were linked to words like G. gob “hollow of hand” and G. gobos “haven” in the contemporaneous Gnomish Lexicon (GL/40). Given these Gnomish forms it is likely the true root was ✱ᴱ√GOPO since initial g- became k- in Early Qenya. In Early Noldorin word lists from the 1920s, however, the related word became ᴱN. cú “bay, cove” < ᴱ✶kópa (PE13/141).
The root ᴹ√KOP appeared in The Etymologies of the 1930s, but Tolkien seems to have abandoned it in favor of ᴹ√KHOP, changing ᴹQ. kópa “harbour, bay” to ᴹQ. hópa/N. hûb “haven, harbour, small landlocked bay” (Ety/KHOP, KOP). In draft maps for Gondor from the 1940s, however, Tolkien gave N. Cobas “Haven” (TI/312, WR/434). Finally, in notes from the late 1960s Tolkien had S. côf “bay” in Côf Belfalas, the Sindarin name for the “Bay of Belfalas”, though the paragraph where it appeared was struck through (VT42/15). As suggested by Carl Hostetter, côf was probably derived from a variant of earlier ᴹ√KOP (VT42/29 note #36), perhaps ✱√KOB.
Thus it seems the conceptual evolution of this root was 1910s ✱ᴱ√GOPO >> 1920s ᴱ√KOPO >> 1930s ᴹ√KHOP >> 1940s ✱ᴹ√KOP >> 1960s ✱√KOB. Given Tolkien’s extreme vacillations on the form of this root, it is probably best avoided for purposes of Neo-Eldarin, but if you do use it I recommend sticking with the derivatives of 1930s ᴹ√KHOP, since those are likely most recognizable to readers of Elvish.
This root was the basis for several “dog” words, most notably S. (or Q.) Huan “Hound”, a name Tolkien used throughout his life. Its earliest precursor was the root ᴱ√SAẆA from the Qenya Lexicon of the 1910s, which had the derivative ᴱQ. fan (fand-) “dog”. In the somewhat earlier Qenya Phonology, Tolkien had ᴱQ. hwan >> huan >> fan, reflecting conceptual shifts in the phonetic development of initial sẉ- in Qenya (PE12/26 note #149). In the contemporaneous Gnomish lexicon the words G. hû “dog” and G. saur “hound, wild dog” seem to be derived from this same root (GL/49, 67). The Early Noldorin word ᴱN. fan(d) “dog” in word lists of the 1920s is probably of similar origin (PE13/143).
In The Etymologies of the 1930s, Tolkien derived N. Huan and a number of other dog-words, first from an (unglossed) extended root ᴹ√KHUGAN, and then from ᴹ√KHUG “bark, bay” (Ety/KHUGAN). In their Reader’s Companion to the Lord of the Rings, Wayne Hammond and Christina Scull said:
> The first element of Huorn could be derived from the base KHUG- “bark, bay”, which appears to be supported by unpublished etymological notes by Tolkien (RC/425).
Hammond and Scull did not further describe these notes so we don’t know whether it actually contained √KHUG, but I think it is likely that these “unpublished notes” refer to the etymology of Huorn on PE17/86, which does not contain √KHUG but does have Q. hú “hound” (the word’s gloss is unclear and might be “heart” according to Christopher Gilson).