Why is the Irish gift of the gab called “blarney”?

Kissing the Blarney Stone at Blarney Castle near Cork, Ireland, is supposed to transfer the gift of gab to the kisser, but the idea that the word blarney meant a smooth talker came from the mouth of Elizabeth I of England in 1602. She had insisted that Dermot McCarthy surrender Blarney Castle as proof of his loyalty, but he kept coming up with excuses — so many excuses, in fact, that the Queen once exclaimed inexasperation, “Odds Bodkins, more Blarney talk!”