They are called Tartans. Here is a website about them: http://www.tartans.scotland.net/

Tartan - an Assyrian word, meaning "the commander-in-chief." (1.) One of Sennacherib's messengers to Hezekiah (2 Kings 18:17). (2.) One of Sargon's generals (Isa. 20:1). Tartan describes a woven fabric that is made up of a particular design, traditionally made in Scotland for a particular clan. The corruption of the word “Plaid” occurred when the Scottish Highlanders wore their Highland cloaks at the time they first moved to America. Plaide was the old Gaelic word for the irregular garment worn by the Scots and was mainly woven in tartan patterns. It actually meant Sheepskin. In America the word became confused with the tartan pattern itself. It eventually evolved as the term to describe any checkered pattern. What a shame! (Stuart Noble) The oldest known piece of tartan is one that was found buried in the ground near Falkirk. It was found in a pot filled with over 1900 silver Roman coins and is thought to be about 1700 years old. It is quite different from many of the colourful tartans that we all know today. Its believed that it was made from the undyed wool, dark brown and light browny/green - of the Soay sheep which once inhabited Scotland and which still can be found on the island of St. Kilda. -------------- Jade figurines wearing tartan hats were found in China, dating back to 3,500 BC or earlier. The Celts wore coats set with a pattern of checks close together and of varied colors, similar in fashion to the Scottish tartan. Tartan patterns have been used in Scottish weaving for centuries. A possible predecessor dating from the 3rd century found near the Antonine Wall and known as the "Falkirk sett" has a checked pattern in two colours identified as the undyed brown and white of the native Soay sheep. The fabric had been used as a stopper in an earthenware pot containing a hoard of silver coins http://www.answers.com/topic/tartan-1 Malcolm MacLean of Scotland wrote Here's to it! The fighting sheen of it, The yellow and green of it, The white, the blue of it, The swing, the hue of it, The dark, the red of it, Every thread of it. The fair have sighed for it, The brave have died for it, The foeman sought for it, Heros taught for it, Honour the wave of it, Drink to the fave of it, The Tartan!