The current castle dates back to the 1400s. I read that Queen Elizabeth I commanded the Earl of Leicester to take possession of the castle from Cormack McCarthy, King of Munster. Every time the
Earl tried to do so, McCormack would suggest a banquet or some other form of delay. Then the Earl would send a missive to the queen at the end of which the castle remained untaken. It is said that the
queen was so annoyed, she remarked that the earl's reports were all "blarney."
Not sure if that is a legend, but it is on the official site of the castle.