What does kissing that blarney stone mean?

The Blarney stone is a piece of folk lore and myth situated at the top of the Blarney Castle.

To complete the ritual, you have to climb to the top of the castle and lean backward over the parapet.

These days there are hand holds and safety devices, but in the "old days" you did this with a trusted friend holding your legs.

You must kiss the stone in this precarious position, for which you are granted the gift of eloquence and persuasion.

If someone says you must have kissed the Blarney Stone as a turn of phase, they are saying you have the "gift of gab" and/or the ability to flatter.