The thick Kerry thing is modern; when I was growing up (some time around the paleolithic era), we said "cute as a Kerryman" - "cute" in Ireland meaning unpleasantly shrewd and cunning; there was another saying, that "A Corkman is a Kerryman with brains".

Cavan people - or Cyaaavan people, as they'd pronounce it themselves - are supposedly mean, all right; Northern people generally are supposedly hard-natured and gritty.

Wicklow ("Wickalla") people are disliked by all Dubliners, traditionally - in fact, by every county - which could possibly be explained by the fact that they used to have a habit of coming down out of the hills and slaughtering the Dubs.

Connemara mountainy men are supposed to be wild but loving. Waterford men ditto. But midlanders in general are seen as dull and stodgy, especially those from Mullingar: "Mullingar heifers, beef to the heels".