On the British Union Jack flag, white represents peace and honesty; red represents hardiness, bravery, strength and valor; and blue represents vigilance, truth, loyalty, perseverance and justice. The term "Union Jack" refers to the flag being a union between three national flags. A "jack" is a small flag flown on a ship's bowsprit, which was the first place the Union Jack was commonly displayed.
The Union Jack is composed of the flags of three patron saints layered one over the other. The central red cross on a white field is the flag of St. George, the patron saint of England. Beneath this, the white X (or "cross saltire," in heraldic terminology) on a blue field represents St. Andrew for Scotland. Layered and slightly offset on the white cross saltire is the red cross saltire representing Ireland's St. Patrick.
The first version of the Union Jack dates to James I's accession to the British throne upon the death of Queen Elizabeth I. Because his crowning represented the first time England and Scotland had been united under one ruler, James also changed the national flag to blend England's and Scotland's flags to create the first British flag, called the Union Flag. In 1801, Ireland was officially added to the British Empire, creating the United Kingdom, and the Irish flag was incorporated into the Union Jack.