An earlier form of the Quenya adjective for “grey”, first appearing in The Etymologies (Ety/THIN). It appears in some later writings as well, notably on WJ/384, and possibly remains a valid variant of the better-known sinda. However, I think it is more likely that Tolkien replaced earlier sindë with sinda. For example, Tolkien changed the Quenya name of Thingol “Grey-cloak” from Sindicollo (with sindë as an element) to Sindacollo (with sinda as an element) @@@.
sindëadjective. grey, pale or silvery grey
sindëgrey, pale or silvery grey
sindë (þ) adj. "grey, pale or silvery grey" (the Vanyarin dialect preserves the older form þindë) (WJ:384, THIN; in SA:thin(d) the form given is sinda, cf. also sindanóriello "from a grey country" in Namárië. Sindë and sinda_ are apparently variants of the same word.) _Stem sindi-, given the primitive form ¤thindi; cf. Sindicollo (q.v.)
sinda (þ) adj. "grey" (PE17:72); nominal pl. Sindar used = "Grey-elves", lit. *"Grey ones"; see WJ:375. Gen. pl. Sindaron in WJ:369. With general meaning "grey" also in Sindacollo > Singollo "Grey-cloak, Thingol" (SA:thin(d), PE17:72; see also sindë, Sindicollo);†sindanórië "grey land", ablative sindanóriello "from/out of a grey country" (Nam); the reference is to a "mythical region of shadows lying at outer feet of the Mountains of Valinor" (PE17:72). However, other sources give sindë (q.v.) as the Quenya word for "grey"; perhaps sinda came to mean primarily "Grey-elf" as a noun. Derived adjective Sindarin "Grey-elven", normally used as a noun to refer to the Grey-elven language. (Appendix F)
†thindë (þindë) older form of sindë, q.v., preserved in Vanyarin (WJ:384, there spelt with the special letter þ, not the digraph th)
Sindicollo (þ) noun "Grey-cloak", title of Elwë (Elu). Sindarin Thingol. (WJ:410, MR:217).(Sindi- in this name is a compound form of sindë, q.v.) Original form Thindicollo (WJ:333). The Silmarillion appendix (SA:thin(d) ) gives Sindacollo.
sir- (1) vb. "flow" (SIR)
mísë (þ, cf. Sindarin mith-) adj. "grey" (used as noun of grey clothes in the phrase mi mísë of someone clad "in grey"). The underlying stem refers a paler or whiter "grey" than sinda, making mísë "a luminous grey" (PE17:71-72)
hiswa (þ) adj. "grey" (KHIS/KHITH, Narqelion)
mista adj. "grey"; see lassemista
lutta- vb. "flow, float" (LT1:249)
lutu- vb. "flow, float" (LT1:249)