Evidence of 1942 usage of "Whole Nine Yards"

I actually read once that the expression came from early football rules in which making a first down required nine yards instead of the modern ten.

I’ve never found anything to confirm this, so I assume it’s another folk tale.

In 1882, the system of “downs” was instituted; at that time, five yards were required to make a first down. In 1906, to open up the game and reduce injuries, the distance required to make a first down was increased to ten yards (other changes were also made). If there was ever any nine-yard requirement, it certainly wasn’t widely recognized, and it would have existed pre-1906, making the gap between the literal source of the phrase and the first known written record 50+ years.

Citey-cite