English Computing Dictionary
Chadless keypunch
(Named after its inventor) A {card punch} which cut
little U-shapes in {punched cards}, rather than punching out a
circle or rectangle. The U's made a hole when folded back.
It was clear that if the Chadless keypunch didn't make them,
then the stuff that other keypunches made had to be "{chad}".
(1997-02-12)