A root in the Qenya Lexicon of the 1910s glossed “know”, but most of its derivatives have to do with “mind” (QL/29). There are quite a few later roots filling this same semantic space, and this root was probably abandoned.
Early Primitive Elvish
isi
root. *know
isi
root. *(light) snow
isifinde-
feminine name. Isifinde-
gisi
root. *know
iþi
root. *(light) snow
aha
root. know
giþi
root. *(light) snow
ŋolo
root. to know
sana Speculative
root. *know
A root in the Qenya Lexicon of the 1910s given as √ISI² with derivatives having to do with “light snow” and Gnomish variants ith- and gith- indicating the true primitive form ✱(Ʒ)IÞI (QL/43). There are no signs of this root in Tolkien’s later writing.