A correlative appearing as sinan or (archaic) †sin in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/109), a combination of ᴹQ. si “this” and ᴹQ. -n(an) “time”. Sinan was translated as “at present” in the Quenya Verbal System (QVS) of this same period (PE22/125).
Qenya
sinde
adjective. grey, pale
sin(de)
adverb. so, so much, *of this degree
sin(an)
adverb. now, at present
hiswa
adjective. grey, grey [of weather], *foggy, overcast; [ᴱQ.] dim, fading
This word is glossed “grey” in The Etymologies, but perhaps means “✱foggy, overcast”, since Sindarin cognate hethw means “foggy, obscure, vague” and related noun hiswë means “fog”. @@@
A correlative appearing as sin or sinde “so, so much” in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of ᴹQ. si “this” and ᴹQ. -n(de) “degree”, so more literally “✱of this degree”.