A verb in The Etymologies of the 1930s glossed “to rend” derived from the root ᴹ√NARAK “tear, rend (tr. and intr.)” (Ety/NÁRAK; EtyAC/NÁRAK).
Noldorin
rista-
verb. to rend, rip
rhista-
verb. to cut
rhista-
verb. to cut
rhista-
verb. to rend, rip
rhest
noun. cut
narcha-
verb. to rend
osgar-
verb. to cut round, to amputate
rhest
noun. cut
A verb appearing in its Noldorin-style infinitive form N. rhisto in The Etymologies of the 1930s as a cognate to ᴹQ. rista- “cut”, both derived from the root ᴹ√RIS (Ety/RIS). In the initial version of this root’s entry it appeared as risto derived from ON. rista- “rend, rip” (Ety/RIS). The original entry was not deleted, and it is not clear if its retention was an oversight or if Tolkien intended both meanings to coexist.
Neo-Sindarin: In Noldorin, an initial r unvoiced to rh, but this was not the case in Sindarin, so its Sindarin form is probably ᴺS. rista-, as suggested in HSD (HSD). I would further assume rista- can mean any of “cut, rend, rip”.