Why is the United Kingdom flag called the Union Jack?

The UK flag, aka the Union Jack, flying in the air.

You may or may not know our flag has evolved as the different countries that now make up to United Kingdom came under the ruling of England. In the 16th century, the flag was known as the British flag or the flag of Britain. It included the red cross of St George (England) and the blue saltire of St Andrew (Scotland). So why is it known as the Union Jack now?

The name ‘Union’ first appeared in 1625. There are various theories as to how it got its name. The most plausible one is that when a small flag was mounted on the front of a warship (and a selected number of other ships), it was called ‘the Jack’.

Evolution of the Union Jack

Sometime around 1674 the British flag became formally known as the ‘Union Jack’ when mounted on a warship and the ship was not in harbour. At the same time the British flag was referred to as the ‘Union flag’ on land. This rule was relaxed by the early 19th century when the sailing term could be used when referring to the national flag everywhere.

The UK's flag. Why is it called the Union Jack?
The first version of the flag was created in 1606, featuring only the English and Scottish flags

The Union Jack was amended in 1801 to incorporate the cross of St. Patrick (Ireland). And if you’re wondering why the Welsh flag was never incorporated into the Union Jack, it is because it was already a principality of England by 1801.

Elements of the UK flag, why is it called Union Jack
Elements of the UK flag

Flags in Wales

In Wales you may see two flags flying, including the red dragon on a green background and the yellow St Davids Cross.

Welsh flag, why is the UK flag called the Union Jack
The Welsh flag
Saint David's flag, why is the UK flag called the Union Jack
St Davids Flag, Patron Saint of Wales

Careful when you place the Union Jack

Make sure you hang the flag up the right way. An upside-down Union Flag is used as a sign of distress. Even worse, it can be seen as an offensive gesture!

Right and wrong way of place the UK's flag, aka the Union Jack

Tip: Always make sure that the red line in the top-left corner is at the bottom of the white cross.