Posted on alt.music.polkas on July 20, 2007. Used by permission.
From what I've gathered from personal research, the polka dance originated in the Czech lands/Bohemia and was done in a manner to mock the way Polish peasant girls danced. From there it spread and became a phenomenon throughout the Austro-Hungarian empire, and eventually wound up, as the Polonaise (Polonez) did, being the big thing in Paris -- I would imagine probably because it's a very informal dance requiring the two partners to be very close (naughty!) and because it sprung from the peasantry as opposed from the top aristocracy like many other popular fads in that era.
Because so many traditional Polish folk songs were also performed in 2/4 rhythm, when such songs made it to America with immigrants, it became very easy, popular, and more familiar and acceptable to "Americans" to simply just classify any given song as a "polka" (instead of a Polish krakowiak, trojak, zbojnicy, wegierka, etc.), as a "waltz" (as opposed to kujawiak, mazurek, etc.) or as an "oberek" (whether in fact they were sztajereks, kujawiaks, mazureks, etc.).
Many of the more common Polish-America polkas we're all used to hearingor playing (e.g., " Psia Krew Polka," "Adam and Eve Polka," "Going to My Girlfriend's," and tons more) have always been, and still are, performed and referred to as "krakowiaks" and other titles in Poland to this day.
Furthermore, don't kid yourself on crediting certain amazing and influential Polish-American polka musicians of the past with writing so many great songs. Many more than you'd ever imagine (at the very least, the melodies thereof) came from Poland and were around before the Wallys, Zimas or Blazonczyks were ever born (no offense to any of the above of course, they're personal idols!). Yes, even "Take Me Baby (North, South, East, West)" came from Poland and is still played there . . . and "Who Stole the Kiszka" from the Ukraine.