I did some on-line searching for this phrase as I never did know what it meant. "Go Way Back..." was apparently a common slang term around 1900. It often meant "Go Way Back and Sit Down", which I think is what was pictured on the chip with the outhouse. It was sometimes used when someone passed gas and stunk up the room, so maybe you kept this chip around to toss toward the offender in the poker game?

It also had something to do with a "Coon Song" written in 1901 which wouldn't pass the "political correctness" test today for songs about blacks.

Here a copy of the sheet music:

and a comment on the piece of music from around the same time.

Anyway, I'd put in the same category as the "Stop Monkeying" chip that also is dated to early 1900's, but GoWayBack is a lot scarcer.