"Samu" of samue means daily works of Zen monks such as cleaning and wood chopping.
The working costumes Zen monks wore were called samue, and it is said that the origin of "samue" is the working costume.
It used to be worn only the longer length (to the knees) of the tops without the pants.
Pants are adopted in order to make it more comfortable and active style later on.
Samue is still worn as working clothes. You can see the Zen monks wearing samue when you visit Zen temples. Because samue is originally made as working clothes, it is very functional, easy to wear and it also allows freedom of movement. Now samue is popular among ordinary people as home wear and street clothes.
Recently, samue is also popular as Zen/meditation uniform. Zen/meditation was brought to Japan from China. It is the idea to concentrate with relaxing your body. Samue is the best uniform for Zen/meditation because it does not constrict your body. It is also worn when having tea ceremony, doing martial arts or playing Japanese traditional instruments.
Compare to kimono, samue has less regulations. There are no rules such as when, where, how to wear. It has variety in materials, so you can enjoy various textures throughout the seasons. Above all, you can appreciate Japanese clothing by the enjoyment of dressing samue. That's the greatest characteristic of samue.