"chad"-- a possible origin

[jdespres at MERRIAM-WEBSTER.COM]

In case anyone is interested, the 1947 citation for "chad" in our
files reads as follows:

The sample tape shown in Figure 2 is of the form produced by the
typing reperforator.  It is known as chadless tape because the
small discs, called chads, which are perforated to form the code
combinations are not cut completely from the tape but are
perforated only sufficiently to permit the chads to rise like small
hinged lids in response to the sensing pins of a transmitter.

RCA Review
Radio Corp. of America Vol. 8 No. 3
RCA Lab. Div. Sept. 1947

This same citation also provides our earliest evidence for
"chadless."  Every other early source I've looked at defines
"chadless" in the same way, i.e., in terms of a tape-punching
method resulting in a lack of chads.  The absence of any reference
to the name "Chadless" in these cites would seem to cast doubt
on the back-formation hypothesis posited as an explanation for
"chad."  Jim Rader mentioned to me that he'd investigated this
hypothesis some time ago by checking patent records for the
name, but came up with nothing.  The "perhaps" derivation in W3
from a Scots word meaning "gravel"  appeared to him to be pure
guesswork.

Joanne Despres
Merriam-Webster