I have heard that in the original wording, Casey Jones's locomotive was described as a "six-eight wheeler of mighty fame." That derived from locos/hogs being classed by the number of bogeys and then the number of drive wheels. As trains gave way to planes, that commonly became "on a big eight-wheeler" instead. (Course the railroad fanatics complicated this by saying nobody ever built a 6-8 hog, but regardless of that, the intent of the writer was changed by those not as familiar with the argot.

I know there have to be many, many more such things out there.

CC