Morihei Ueshiba

Morihei Ueshiba, founder of Aikido.

Ueshiba developed Aikido primarily during the late 1920s through the 1930s through the synthesis of the older martial arts that he had studied. The core martial art from which Aikido derives is Daitō-ryū Aiki-jūjutsu, which Ueshiba studied directly with Takeda Sokaku, the revivor of that art. Additionally, Ueshiba is known to have studied Tenjin Shin'yō-ryū with Tozawa Tokusaburō in Tokyo in 1901, Gotōha Yagyū Shingan-ryū under Nakai Masakatsu in Sakai from 1903 to 1908, and judo with Kiyoichi Takagi in Tanabe in 1911.

Ueshiba moved to Hokkaidō in 1912, and began studying under Takeda Sokaku in 1915. His official association with Daitō-ryū continued until 1937. However, during the latter part of that period, Ueshiba had already begun to distance himself from Takeda and the Daitō-ryū. At that time Ueshiba was referring to his martial art as "Aiki Budō". It is unclear exactly when Ueshiba began using the name "Aikido", but it became the official name of the art in 1942 when the Greater Japan Martial Virtue Society (Dai Nippon Butoku Kai) was engaged in a government sponsored reorganization and centralization of Japanese martial arts.

You can find more about Morihei Ueshiba here.