Etymology Online says this expression means a “remarkable person or thing…” and its origin was “…perhaps from an old song, ‘Dandy Jim of Caroline’ (1840s).” I was disappointed with the lackluster description of the origin, but decided to stick with it because “A Jim Dandy” was the headline of the sports report about Colorado State University’s victory in the “Mile High Showdown” football game over Colorado University September 1, 2012.