1590s, from notch (n.). Earlier verb (before misdivision) was Middle English ochen "to cut, slash" (c.1400). Related: Notched; notching.
An indentation at the edge of a structure; an incisure.
An upstroke or peak on a pulse tracing.
[first sense fr use of the term in cricket, and influenced by the cowboy tradition of filing a notch in the handle of one's pistol for each man killed]