 It may come from the 'jack-et' of the English or Scottish soldiers, or from the name of James I who originated the first union in 1603.Even if the term "Union Jack" does derive from the jack flag, after three centuries, it is now sanctioned by use and has appeared in official use, confirmed as the national flag by Parliament and remains the popular term.Winston Churchill was Prime Minister of the United Kingdom from 1940 to 1945 and he referred to the flag of the United Kingdom as the Union Jack.