Blarney Castle is famous for its stone, which is traditionally believed to have the power to bestow eloquence on all those who kiss it. The stone itself is set in the wall below the battlements and to kiss it, one has to lean backwards (holding onto an iron railing) from the parapet walk.

The stone was reputed to have been that mentioned in the Bible as "Jacob's Pillow" and was supposed to have been brought to Ireland by Jeremiah the Prophet. It was more likely to have been brought back during the Crusades which legend applies also to the Stone of Scone now at Westminister Abbey.

Another tale was that McCarthy was given the story of the stone by an old woman whom he saved from drowning. This lady turned out to be a witch. As a reward, she told him the secret of a stone in the castle which would give him the gift of eloquence in return for a kiss. Wherever the truth lies, tradition has it that once kissed the stone bestows the gift of eloquence.