A word for “dusty” in the Gnomish Lexicon of the 1910s, simply an adjectival form of G. thith “dust” (GL/73).
Gnomish
thith
noun. dust
thithrin
adjective. dusty
hant
adverb. thither
sitha
adjective. this
entha
adverb. there by you, thither
A noun in the Gnomish Lexicon of the 1910s glossed “dust”, appearing below other forms like G. thisin “parched, withered” (GL/73). The latter is clearly a cognate of ᴱQ. sisin from the contemporaneous Qenya Lexicon, and hence is derived from the root ᴱ√SISI as it appeared in that document (QL/84), though its Gnomish derivatives make it clear the actual root was ✱ᴱ√ÞISI.