A noun in The Etymologies of the 1930s glossed “hound” derived from primitive ᴹ√KHUGAN; in the second version of this entry the root became ᴹ√KHUG “bark, bay” and Tolkien only said that N. Huan was a dog-name, though its cognate ᴹQ. huan still meant “hound” (Ety/KHUGAN). This word was indeed used as the name of the great Valinorian hound Huan, which Tolkien established very early (LT2/21) and retained for his entire life (S/142).
Possible Etymology: It is hard to explain why the primitive short ŭ in huan did not become o as usual in Noldorin and Sindarin. Perhaps the primitive form was actually ✱khūgan in the Noldorin/Sindarin branch of the language. Tolkien did frequently write the name as Húan in later writings (RS/183; WJ/62 and forward).
Conceptual Development: In Tolkien’s earliest writings, ᴱQ. huan “dog” was a Qenya word, and its nearest Gnomish equivalents were G. hû “dog” and G. saur “hound, wild dog” (GL/49, 67), all derived from the early root ᴱ√SAẆA (QL/82). The form ᴱN. fand or fan “dog” appearing in Early Noldorin Word-lists of the 1920s was probably also related (PE13/143). By The Etymologies of the 1930s, it seems Huan was a Noldorin name, and it may have remained so in Sindarin of the 1950s and 60s, but since its Quenya form was identical it is hard to know for sure.
The great hound who helped Beren and Lúthien against the forces of Morgoth (S/142). His name is derived from the same primitive form ᴹ✶khugan as ᴹQ. huan “hound” (Ety/KHUGAN). Given that he was originally a Valinorian hound, it is possible his Sindarin name is simply adopted from Quenya.
Conceptual Development: The name ᴱQ. Huan appeared in the earliest Lost Tales (LT2/21) and remained constant through all Tolkien’s later writing, though its language ultimately changed from Qenya to Sindarin. The name N. Huan appeared in The Etymologies from the 1930s, which is the source of the derivation given above (Ety/KHUGAN).