There are various theories on the origin of 'karate'. But most martial arts historians hold the following events to be historically correct.
In the 1600s the Empire of Japan conqured the island nation of Okinawa. The Mighty Shoguns and Warlords found the Okinawan people to be a nation of fierce warriors and excellent fighters. As a way of preventing retaliation from the Okinawan people. The Japanese banned and confiscated all weapons. The natives had no alternative but to develop and practice the art of 'empty handed fighting' as self defense. The Japanese translation for this is (karate). Therefore empty handed (martial arts) has developed nearly 350 years into the art of (karate).
In addition the Okinawan people are also credited with the adept use of simple farm tools and turning them into weapons. The martial arts weapon (nunchuku) was originally used to pound wheat into grain. The Bo Staff was used to carry two buckets of water across the back and the sai was used to till the soil and plant seeds.
Many modern Martial Arts have a strong karate Heritage and in itself it can be both an efficient means of (self defense) or a devastating way of combat.