By surface analysis, не- (ne-, negating particle) + ряз (rjaz, “slash”). Synchronically, probably a conflation of Proto-Slavic *nerězь (“uncut”), whence dial. Russian нерезь (nerezʹ, “uncastrated boar”), and *kъnorzъ (“male animal”), according to Schuster-Šewc, possibly a compound of *kъmn- (“stock, root”) + *orzъ (“testicle”).