From Wikipedia

The Fighting Scots

A Scottish regiment is any regiment (or similar military unit) that at some time in its history has or had a name that referred to Scotland or some part, thereof, and adopted items of Scottish dress. These regiments were and are usually a product of the British Empire, either directly serving the United Kingdom, serving as colonial troops, or later as part of Commonwealth country military establishments. Their "Scottishness" is not necessarily due to recruitment in Scotland nor any proportion of members of Scottish ancestry. Traditionally, Scottish regiments cultivate a reputation of exceptional fierceness in combat and are often given romantic portrayals in popular media. Within Scotland, itself, regiments of the Scottish Lowlands did not adopt as strong a "Scottish" (specifically Highland Scottish) character until the late Victorian Era.