The Union Flag, popularly known as the *Union Jack, is the national flag of the United Kingdom. It is the British flag.
It is called the Union Flag because it symbolises the administrative union of the countries of the United Kingdom. It is made up up of the individual Flags of three of the Kingdom's countries all united under one Sovereign - the countries of 'England, of 'Scotland' and of 'Northern Ireland' (since 1921 only Northern Ireland has been part of the United Kingdom). As Wales was not a Kingdom but a Principality it could not be included on the flag.
The following pages will tell you how the Union Flag (Union Jack) came to be the UK's national flag and the making of the United Kingdom. Pay no heed to the picky people fair question pitty they couldnt just answer it. Sorry I no longer serve but Union Jack seems fair to me.
The Union Flag is commonly known as the Union Jack, although the exact origin of the name is unclear. One explanation is that it gets its name from the "jack staff" of naval vessels from which the original Union Flag was flown. www.number-10.gov.uk
Historian David Starkey said in that Channel 4 tv programme that the Union Flag is called 'Jack' because it is named after James l of Great Britain (Jacobus , Latin for James), who introduced the flag following his accession to the throne