The Google Books search for
"cornhole" between 1900-1965 reveals usage as anal sexing or people's names. The earliest sex reference in their list seems to be 1951 with "Don't let him cornhole you!" Moving the search to
1995-2005 begins revealing references to the game. All other date ranges previous involve anal sex, the anus, someone's name or a literal hole in the ground for corn. (I checked.) Naturally, this doesn't mean much about its out-of-book uses but it does give
some metric.
Alternative sources include the
American Cornhole Association with an unconvincing:
It has been said that the game originated in Germany in the 14th century, and then was rediscovered in the hills of Kentucky over 100 years ago.
And an
article in (the Cincinnati?) Enquirer and the
Corn Hole Game Association which essentially agree that history is contested and no date is available.
The game itself has probably been around as long as it was feasible to put corn or other seed into a sack and toss it at something. While the name
cornhole would probably have been independently coined all over the place, its universal acceptance as a name of the game doesn't appear much earlier than the 2000s. There are often
tales of people using the name earlier but apparently none of them ever decided to publish a book.
Given its other usage having already been published in various forms it seems safe to say the word's primary meaning during the mid-1900s was significantly less innocent than a game played with sacks of corn. Whether anyone was calling the game
cornhole then or not, that was mostly likely
not the meaning of the word.
In other news, a 500 reputation bounty may not be enough to sift through pages upon pages of Google book matches relating to anal sex.
https://english.stackexchange.com/questions/23488/what-is-the-etymology-of-cornhole