hmmm, different to the story i know and grew up with.
I used to live in West Cork, (South West Ireland) near a town called Skibbereen. My family still live there.
Anyways there's a beautiful lake called Lough Ine and on this lake is a small island. On the island is O'Driscoll castle which is where the king who had asses ears was said to have lived.
The story goes that he killed every barber that cut his hair and threw them in the lake so his secret was safe. One day a barber threw the cut hair into the lake. The hair fell to the bottom of the lake and later a reed grew from it.
When a musician from the castle was sitting by the lake, he fashioned a whistle out of the reed. As he played the whistle all that could be heard was "the king has asses ears! the king has asses ears!" and so the secret was out!
thats the island, you can make out the remains of the castle, its covered in deep green.
when we were kids we used to row out there, when we were bigger kids we swam