notch (n.)
1570s, probably a misdivision of an otch (see N for other examples), from Middle French oche "notch," from Old French ochier "to notch," of unknown origin. Said to be unconnected to nock.
notch (v.)
1590s, from notch (n.). Earlier verb (before misdivision) was Middle English ochen "to cut, slash" (c.1400). Related: Notched; notching.