What's the meaning of the phrase 'Union Jack'?
The Union Jack is the popular name of the national flag of the United Kingdom.
What's the origin of the phrase 'Union Jack'?
Two subjects that arouse passion more than most are language and national identity and, here in the UK, these collide at the name of the national flag. Spare a thought for my welfare as I wade gingerly into a muddy pond teeming with crocodiles with a particular taste for etymologists.
What's the flag called? It's the Union Jack of course. Pause for an intake of breath amongst purists; "No, it's the Union Flag!".
Whether you prefer 'flag' or 'jack', most agree on the union part of the name. I say 'most' as even calling the place I live the United Kingdom will raise some hackles. I often get mail along the lines of "You live in England! England, geddit, not the UKay!".
Nevertheless, let's press on and try to explain the oddly named standard, the Union Jack. The 'union' part is straightforward. The flag originated as a visual representation of the various political unions of the countries that formed the United Kingdom of Great Britain and Northern Ireland, the present design being established in 1801.
(An aside for those who aren't quite sure what Great Britain is. Britain is the little green island to the north of France, originally called 'great' to distinguish it from what is now called Brittany, which was in the Middle Ages also called Britain. Brittany is now sometimes called Little Britain, which can be confusing as the popular TV show, Little Britain was about Great Britain not Brittany ...and this little tangent was supposed to clarify things. Let's get back to the plot.)
The flag was formed by photoshopping the crosses of the patron saints of England, Scotland and Ireland - St. George, St. Andrew and St. Patrick. Wales was already a principality of England by this point so didn't get visual representation on the flag.
So, that's 'Union'. Now to the tricky part - 'jack' or 'flag'. The OED defines 'jack' in this way:
A ship's flag of smaller size than the ensign, used at sea as a signal, or as a mark of distinction; spec. the small flag which is flown from the jack-staff at the bow of a vessel (formerly at the sprit-sail topmast head), and by which the nationality of a ship is indicated, as in British jack, Dutch jack, French jack.
Both Union Flag and Union Jack are widely accepted as referring to the national flag of the United Kingdom. In reality, although many will argue that they KNOW (and they probably will use capital letters) which is the proper name, neither Union Jack or Union Flag is formally adopted and so you are free to use either.
The Union Jack is flown from the jack-staff, which is a spar on the bow of a sailing ship, and some say that the only time that the flag should be called the Union Jack is when it is flown from a ship's jack-staff. If you like you can opt for über-pedantry and call it the Union Jack Flag.
For and against we have:
'Union Flag' is first known in print in 1634 and 'Union Jack' is first found in 1674, so 'Union Flag' supporters may say that it had the name first and that 'Union Jack' is just a nickname.
Union Jack is more widely used and so has the advantage that everyone around the world will know what you are talking about.
Now, I'd just better check that image of the national flag is the right way up or I'll really be in trouble.
See also: other 'Jack' phrases.