Sindarin name of the great spider-demon (LotR/723, S/73). The initial element of her name is probably ungol “spider” but the meaning of the second element is unclear. It may simply be an adaptation of her Quenya name Q. Ungoliantë (Ety/UÑG).
Conceptual Development: In the Gnomish Lexicon from the 1910s, this name first appeared as G. Gungliont “The Spider of Night” (GL/43), but this was rejected and replaced by Ungweliont or Ungoliont (GL/75), a change that was also made in the earliest Lost Tales (LT1/156). At this stage, the initial element ungwi meant “spider” (GL/75). In the Lays of Beleriand from the 1920s and Silmarillion drafts from the 1930s, the name was changed to Ungoliant (LB/132; SM/16, 91), though later in the drafts her name was generally replaced with its Quenya equivalent ᴹQ. Ungoliante (LR/230, 299).
At this stage, the name was frequently translated “Gloomweaver” (SM/16, 91), and in The Etymologies, N. Ungoliant was an adaption of her Quenya name with the same meaning, as noted above (Ety/UÑG). Here, the initial element Ungo- was related the root ᴹ√UÑG having to do with darkness and the final element -liant was related the root ᴹ√SLIG from which ᴹQ. liante “spider” was derived (Ety/SLIG). In Lord of the Rings drafts from the 1940s, Ungoliant was also briefly considered as a name for Shelob (WR/196).
Given Tolkien’s later use of S. ungol as the Sindarin word for “spider”, it seems that he reversed the meaning of the two elements of this name again, but there is no indication of what the second element of the Sindarin name might mean in any of the published materials.
Ungoliantë fem. name "Ungoliant" (the Spider, ally of Morgoth); also Ungweliantë (UÑG, DYEL, SLIG)