The toga was originally an
Etruscan variation of the Greek
himation, being inherited from the early years of the
Roman era, before the
Republic, when the Latins (as they are known ethnicly) were under the rule of Etruscan kings. The Etruscans invented the toga by cutting off two of the himation's corners, so it would be long enough to stay in place, while reducing weight. This
trapezoidal design was later modified by the Romans to become the
semicircular design it is known as now. The toga was originally a
military uniform, and thus it was restricted to Roman citizens;
citizenship originally depended on one's
service in the
military.
Over time the toga grew in size. At one point, a double version was developed, which was basically a circle folded into a semicircle and then draped about the body. In this version, a special fold would be created, called the sinus, and would act like the modern pocket. As the toga grew in size, it was less and less used in day-to-day affairs, eventually being restricted to special occasions or ceremonies.
In the early Republic, the toga ceased to be a purely military garment and became the apparel of the common citizen. The toga grew to its largest size during the times of the Antonines, while in the late empire, it shrank into a form that was somewhat like a cape worn only by the Consuls, and then only when giving the starting signal for chariot races.