fkovalski
My Dad always used to say the same thing, so I looked it up (Google is a wonderful thing). I found this:
Fair to Middlin' came from the Cotton
Markets of years ago. Fair to Middlin' probably
came to this country from Scotland. When they
were Grading the cotton in the warehouses, the
"grader" would go down the rows, saying about
the bales, Fair, Good, Middle. . all grades of
cotton. Some fell in a wider category, so they
graded it Fair to Middle... "fair to middlin'
As with all things Internet, I cannot vouch for it's authenticity or accuracy...