Blarney Castle was originally a timber hunting lodge built in the 10th century, which was replaced by a stone castle in 1210. The present day construction was completed by Dermot McCarthy, King of Munster in 1446. The Castle remained the ancestral stronghold of the McCarthy family until the arrival of Oliver Cromwell with cannon guns in 1646. Fifteen years later with the arrival of King Charles II on the English throne saw the return of the McCarthys to the Castle.

Following the Battle of the Boyne in 1690, all Irish chiefs were stripped of their powers and the McCarthys were again forced to leave Blarney Castle. The Castle was sold to Sir James Jefferyes, Governor of Cork in 1703. Now mostly ruins the Castle is owned and managed by the Trustees of the Blarney Castle Estate.

Queen Elizabeth I coined the phrase due to her exasperation with Lord Blarney's ability to talk endlessly without ever actually agreeing to her demands. Whenever someone became too flattering or long winded she would exclaim they were "full of the Blarney!"