Allegedly invented by the
6th century B.C. poet
Sappho, the chlamys was the ancient version of a
poncho. The cloak was a variation of the
Thessalian cape, made from a circular or square piece of linen or wool, and was worn alone or over a
chiton by respectable men. It was ideal for hunting, riding, fighting and travelling, as the draping was loose and allowed for much movement.
The chlamys was especially popular in the 7th-5th centuries (the classical period) and was one of the smallest garments for men, measuring 6 feet across and only around 2 feet long. The cloth was folded in half around the body and fastened at the front or at the right shoulder, covering one arm and exposing the other. The wearer of the cloak would have to be immodest - it exposed both legs and genitalia. (The chlamys is still worn in some naturist communities.) In later centuries, the chlamys lengthened and became the himation.
When travelling the chlamys would be worn alone, accompanied perhaps by a petasos (wide-brimmed hat), and as its main purpose was for comfort it would be be left beige, the natural colour of its fabric. The messenger god Hermes was often depicted wearing costume like this.
The word "chlamys" is from the Greek khlamus, meaning literally "cloak draped around the shoulder". This word has the same origin as "chlamydia"; its definition also describes the behaviour of chlamydia trachomatis bacteria around cells.
For a picture of the chlamys in action, see http://www.costumes.org/history/greece/heuzey/64.jpg or (cough) http://www.esptec.com/Naturist/#chlamys.