(This is pretty slim and therefore incomplete and biased.)
Origin of "Aikido" ∞
The word 'Aikido' was originated by grandmaster Morihei Ueyshiba. As a youth, harassment encountered by his father kindled his interest in martial arts. Subsequently, association with a spiritual leader influenced his religious attitude. Finally, his father demise prompted his spiritual quest.
While perfecting his martial art, several words were chosen to name it. The earlier names included the syllable 'bu' (martial art). As he advanced in his religious pursuit, he finally settled on the word 'Aikido' to reflect his ultimate understanding of life and the universal realm. The syllable 'bu' was omitted.
He managed to originate a sophisticated martial art in which he demonstrated successfully to convey its intrinsic power.
Due to the conservative tradition of those days, practices were often done with minimum instruction. The emphasis was on rigorous training. Further, due to his religious background, his teachings of Aikido were often full of mystical connotations arising from his ascetic training. Thus the power, which accompanied the sophistication of Aikido as a martial art, was not fully understood nor inherited extensively.
Founder of Ki-Aikido ∞
In the meantime, his top disciple, Sensei Koichi Tohei, steadfastly went about figuring out the essence of his master's achievement. It required a keen insight as well as the arduous practice of other disciplines to polish his understanding of Ki.
As a university graduate, the academic education provided him with the basis to study everything in a scientific manner.
Coupled with his astute ability, he successfully deciphered the natural phenomena of Ki and subsequently founded what is now internationally known as 'Ki-Aikido'. The prefix denotes Sensei Tohei's emphasis on Ki development.
Sensei Koichi Tohei's greatest gift to the world is in his simplistic Ki curriculums, which he painstakingly compiled over the decades so that we can benefit from his legacy. This includes Aikido with mind and body coordinated. The crux of all his programmes is based on scientific explanations of the natural phenomena, including Ki.
It is indeed a worthy treasure to inherit from him.