Takagi means "tall tree," while yōshin translates as "spirit of the willow tree." It is so named because a willow tree is flexible and thus harder to break.
According to the Bugei Ryuha Daijiten, the head of the Bujinkan organization, Masaaki Hatsumi is a lineage holder of Takagi Yōshin-ryū (see ancestral schools) transferred to him in the middle of the 20th Century by his teacher Takamatsu Toshitsugu. The Bugei Ryuha Daijiten has entries bearing the name of Hatsumi below his teacher Takamatsu Toshitsugu for Takagi Yoshin Ryu as well as other ryu. (Please note that if you look at the entry for Takagi Yoshin Ryu, you are referenced to the listing for Takagi Ryu (which was also listed in the Kakutogi no Rekishi of 1843). Hatsumi is one of six individuals listed below Takamatsu Toshitsugu in this listing. This is because Takamatsu Toshitsugu split his scrolls among several students, including Fumio Akimoto and Kimura Masaji, among others.
In 1843 Takagi Ryu was mentioned in the Kakutogi no Rekishi (“The History of Fighting Arts”), p.508-517. Although details of the ryū were omitted, the publication states, "Even though they are not mentioned in this particular periodical, there are several schools that are well-known for being ‘effective arts’ (jitsuryoku ha)." Among the schools listed in this section are Gyokko Ryu, Gyokushin-ryū Ninpō, Gikan-ryū Koppōjutsu, Kukishin Ryu, and Takagi Ryu, and Asayama Ichiden Ryu (which in not part of the Bujinkan’s nine schools but was studied by Hatsumi via Takashi Ueno).
Yōshin-ryū, founded in the latter part of the seventeenth century by Akiyama Shirobei Yoshitoki is a traditional school of Japanese koryu bujutsu. Takagi Yoshin Ryu was allegedly founded by Takagi Oriuemon Shigenobu (1625 - 1711). The second master of Takagi Yoshin Ryu, Takagi Umannosuke, was also the first sōke of Takagi Ryu and received menkyo in Takenouchi Ryu Jujutsu as well. The Takagi Yoshin Ryu style is also related to Hontai Yoshin Ryu.