Do ( pronounced "doh", Think of Homer!) means road, way, path or method.

In Chinese it is sometimes written Tao - "The Way". 

Some practitioners of karate subscribe to the idea that karate is a way of life for them, and refer to it as "Karate- do". This way of thinking was made much more popular by Funakoshi naming his autobiography ‘Karate-do, My Way of Life’. 
He never refers to the way he does karate as Karate-do, just karate, probably meaning Karate-do is the way he relates practical karate to his everyday life, I.e. karate-do and the way karate is done are not the same thing.

The idea that pure technique is uppermost, is the forefront of Shotokan karate, ideally meaning one properly performed technique will finish off an opponent. If you are being attacked by several opponents at once, it would probably not be the best time to start grappling or fighting on the floor. It would be essential that you are able to finish off each attacker quickly, and with as little energy as possible by using no more than one technique per person. In Shotokan karate training, each basic move is repeated many, many times, to maximize its effect when used in a confrontation situation.

Modern karate was brought to Japan in 1922 by Gichin Funakoshi. The history of karate however stretches back to the Ryukyu Islands off the coast of Japan, known as Okinawa. Here, the predecessor of modern karate Okinawa-te was performed.

The origins of Okinawa-te are not fully known but some of the influence for this may have came from China and it was developed more fully because of the ban of weapons in Okinawa in the 15th century.

There were two main styles of Okinawa-te, Shuri-te (Shorin) and Naha-te (Shorei). Styles of karate such as Shorin-Ryu where derived from Shuri-te, whilst styles such as Goju-Ryu were derived from Naha-te. It is said by some that Gichin Funakoshi merged Shorin and Shorei to form Shotokan. However Gichin Funakoshi never studied Naha-te and the kata which he eventually included in Shotokan were from Shuri-te suggesting that the combination of these styles is not correct.

In 1922, Gichin Funakoshi went to the mainland Japan to give a demonstration of karate to the All Japan Athletic Exhibition. After this he was asked to give a demonstration at the Kodokan Judo Hall to Jigoro Kano (The founder of Judo), and the demonstration was well received.

After this, Master Funakoshi started teaching karate in a small dining hall in the Meisojuku, and after a couple of years he began teaching at other institutions with karate clubs opening at several universities.

In 1939 due to the success of the clubs a new central dojo was formed and opened by Funakoshi, over the door was hung a plaque which read "The hall of Shoto" - Shotokan, Shoto being the pen name Gichin Funakoshi used to sign his poetry. During the Second World War Yoshitaka (his son) was killed and the Shotokan dojo destroyed.
Japan was devastated after the war and Japanese martial arts were banned by the occupying allied forces.