This word is unattested, but there is indirect evidence for it as an element of walwistë “change of mind” (PE17/189). This word likely contains the archaic form †wistë from before the change of w- to v-. Its modern form would be ✱vistë. If you accept inwist- as the stem form of inwis “change of mind”, it likely contains †wistë as well.
There is another attested word wirnë with the gloss “change” (PE17/191), but I think it is likelier to be the archaic form of the strong-past tense of the verb virya- instead of a noun.
wirnë noun? "change" (PE17:191)