This is one of the most amazing video optical illusions using color contrast throw dancing, for the first time you might think that there are dancers but olnly their legs is appear. This type of dance is a German dancing under the title Strumpfhosentanz - a German word which means "Tights Dance"
If you google about the keyword "Strumpfhosentanz" you will find a lot of videos of this type of dancing.
The song is officially German and is called "Hiss - TANZ" and after some checking it may be that there is a heavy German influence in the Cajun music I have heard. Turns out the most prized accordions in that are the German. However I doubt the Germans play the washboard, I could be wrong.