The Oxford English Dictionary's word of the day is saltire:
An ordinary in the form of a St. Andrew's cross, formed by a bend and a bend sinister, crossing each other; also, a cross having this shape. Hence, in saltire: crossed like the limbs of a St. Andrew's cross.
He was the first of the apostles of Jesus. Andrew had been a disciple of John the Baptist, he recognised Jesus as the Messias. He brought his brother, Simon (Peter), to Jesus. They fished and lived together. They went with Jesus; and as Jesus, they too, were crucified. Jesus on some sort of T, Peter on an upside down T, and Andrew on an X, hence the shape of his flag. The date of his martyrdom was 30 November 60, in Patrae, Achaia, Greece.
In the last few years, there has been some controversy, concerning the advocacy of a greater public celebration of the day in Scotland, some nationalistic, some religious. It is of some political posturing of which flag is flown: Andy’s saltire, the scot’s ancient national flag vis-à-vis the british Union Jack.
Of all the european countries, it seems, Scotland has the fewest holidays. Some want Saint Andrew’s day as a full legal holiday. Some want a national celebration, in honor of the saint. But, how did the scots develop an affection for Andrew? Well, in the eighth century, some* of the relics (bones) of Andrew made it to the pictish lands. A town developed around the monastery and church there. Not long after, the picts and the scots coalesced into a combined kingdom and nation. The primacy, of the scottish church, was transferred to Abernethy from Dunkeld, and finally to Saint Andrews.
In the late middle ages, the cathedral of Saint Andrew became the largest building in Scotland. The university also came and slowly grew from 1411. Then John Knox inspired a mob to wreck and sack the cathedral and other buildings, in 1559. Here the relics were lost, probably destroyed in the glee of vandalism and sacrilege. The stones of the building were scavenged for other projects, and a great deal of the town was in ruins.
* Often relics have been divided and dispersed. Most of Andy’s bones are in the Duomo (Cathedral) of Saint Andrew in Amalfi, Italy.