_ n. Zoo. _Q. hlóke, lóke. (s)lōkō << (s)lōkā.
Sindarin
lhûg
noun. reptile, snake, serpent, worm, reptile, snake, serpent, worm, *lizard; [N.] dragon
lhûg
noun. snake, serpent
lhûg
noun. hlóke
lhûg
dragon
lhûg (construct lhug; with article ?i thlûg or ?i lûg the lenition product of lh is uncertain) (snake, serpent), pl. lhuig (?i luig), also amlug (pl. emlyg).
lhûg
serpent
lhûg (construct lhug, with article ?i thlûg or ?i lûg the lenition product of lh is uncertain) (snake, dragon), pl. lhuig (?i luig).
lhûg
dragon
(construct lhug; with article ?i thlûg or ?i lûg – the lenition product of lh is uncertain) (snake, serpent), pl. lhuig (?i luig), also amlug (pl. emlyg).
lhûg
serpent
(construct lhug, with article ?i thlûg or ?i lûg – the lenition product of lh is uncertain) (snake, dragon), pl. lhuig (?i luig).
A noun in Quenya Notes from 1957 (QN) derived from primitive ✶(s)lōkō “reptile, snake, worm” based on the root √LOK “bend, loop”, so presumably having a similar meaning (PE17/160). Christopher Tolkien also had lhûg in The Silmarillion appendix, but gave it the glosses “snake, serpent” (SA/lok).
Conceptual Development: In the Gnomish Lexicon of the 1910s, Tolkien had G. ulug “dragon” (GL/74), and in the contemporaneous Official Name List for the Lost Tales and the Name-list to the Fall of Gondolin he had G. lug or lûg “snake” (PE13/105; PE15/28). In The Etymologies of the 1930s, Tolkien had N. lhûg “dragon” under the root ᴹ√LOK “great serpent, dragon” (Ety/LOK), where initial *l* was unvoiced to *lh* as was usual in Nodorin. This was no longer true of Sindarin of the 1950s and 60s, so Sindarin lhûg required a primitive from ✶slōk- and a corresponding Quenya form of hlócë.
Neo-Sindarin: Given the breadth of its glosses, I would assume this word can apply to any sinuous reptilian creature with or without legs, including lizards, snakes and dragons.