Dick Swain after hearing me sing this had mentioned it comes from the 'War of Jenkin's Ear'.
Copied from: Wikipedia, the free encyclopedia.
The War of Jenkins' Ear was a conflict between Great Britain and Spain that lasted from 1739 to 1742.
Under the 1729 Treaty of Seville, the British had agreed not to trade with the Spanish colonies. To verify the treaty, the Spanish were permitted to board British vessels in Spanish waters. After one such incident in 1731, Robert Jenkins, captain of the ship Rebecca, claimed that the Spanish coast guard had severed his ear, and in 1738 exhibited it to the House of Commons - hence the name of the conflict. The British Prime Minister, Robert Walpole, reluctantly declared war on October 23, 1739. Google has plenty more on this.