Where did the name union jack come from?

The name "Union Jack" originated from the union of the flags of England, Scotland, and later Ireland. The term "jack" refers to a flag flown at the bow of a ship, and the flag is only officially called the Union Jack when used in a maritime context. The design symbolizes the unity of the countries within the United Kingdom, with the cross of St. George for England, the saltire of St. Andrew for Scotland, and the saltire of St. Patrick for Ireland.