Kerry, or Irish polkas, bear only a limited relationship to the more standard forms of polkas which spread all through Europe and America from 1850ish on. Irish musicians played both types(and the hybrids), which confuse the issue. Another element of confusion is that many four bar reels(in Ireland and thoughout Britain)were readily coverted into 8 bar polkas by playing them slowly, but with a speeded up beat.
(This point is possibly incomprehensible to non-trad musicians. As an example, think of the well known dance tune "My love is but a Lassie Yet". To play it as a polka, eg for the Cumberland Square Eight, the notes Love Is But A Lassie Yet would go oompa oompa oompa pa. In the original(?) reel tempo, those same notes would go faster, but with a slower underlying basic rhythmm, as diddle diddle diddle did). This is how many polkas were"manufactured" in the far northwest of Europe, by refiguring existing tunes. Just as waltzes were similarly constructed by slowing down jigs.)
    Thus polka tunes, for example, can often predate the dance, and the name Polka. This makes research into tune origins extremely complicated, and also very tendentious when pure research comes up against national pride, as is inevitable in this murky field.
   For an interesting(possibly?) digression on the arrival of polkas in the sliabh luachra, try my article on William Irwin. But I should warn you, it a longish article, and the polka reference is only a few lines!