The Scottish Flag (or Saint Andrew's Cross) is rectangular, with a blue background and a white cross. The white cross symbolizes the X-shaped cross used by the guardian saint of Scotland when Saint Andre died. The history of this flag can be traced back to the 9th century AD. it is still the oldest national flag in the world. If only the title of sovereign state is counted, it belongs to danibro of Denmark.

The X-shaped cross, also known as Saltire, is used as the flag of many countries or regions. King James VI of Scotland inherited the throne of England in 1603. Since then, the two kings have merged, so he later merged the flags of the two countries in 1606, overlapping the flag of St. Andre and the flag of St. George of England. Later, the flag was formally adopted in the United Nations act of 1707 and became the flag of the United Kingdom. In 1801, it joined the St. Patrick flag of Ireland and became the current meter flag.

Source: @dbishoptattoo