Gnomish
glis
adjective. sweet
glist
noun. sugar
glisc
adjective. fond of sweets; fond of saying sweet or flattering things, suave, flattering
glisca-
verb. to have a sweet tooth, like sweet things
glissith
noun. sugar
neglis
noun. honey
gilt
noun. a gleam
gur
adjective. sweet
gûri
adjective. sweet
tintiltha-
verb. to twinkle
In the Gnomish Lexicon of the 1910s the word for “sugar” was G. glist along with a longer variant G. glissith where the second element was G. thith “dust” (GL/39). The word glist was likely derived from the early root ᴱ√LISI “sweetness” (QL/54-55).
Neo-Sindarin: Since √LIS survived as the basis for “sweet” words in Tolkien’s later writings, I’d retain ᴺS. glist “sugar” for purposes of Neo-Sindarin.