Hitokiri Battou-sai translates to Assassin Sword-drawing Master.
Hitokiri (Assassin) was also a title/nickname given to people feared for their killing skill.
A Sakaba sword is one with the blade on the reverse side.
Kenshin's character is based loosely on the actual Hitokiri Kawakami Gensai. Kawakami, one of the four great Hitokiri of the era, was often mistaken for a girl at first glance. However, his actual personality was quite cold and calculating, and he was said to have been the most terrible of the four Hitokiri.
In the manga, Kenshin is a Choshuu patriot, Himura Battou-sai, of the Hiten Mitsurugi style of kenjitsu.
The Meiji Restoration was a coup lead by the Satsuma and Choshuu domains to overthrow the Shogunate and restore the Meiji Emperor to power. Satsuma, Choshuu, and Tosa were the three largest domains.
The Satsuma and Choshuu were traditional rivals of each other, each trying to be number one among the domains. However, with the Shogunate in the weakest state ever, the Satsuma and Choshuu allied and their combined military strength was able to bring about the overthrow of the Shogunate and the restoration of the Meiji Emperor. Historically, this groundbreaking alliance between these rival domains was first forged in a meeting between Satsuma leader Saigo Takamori and Choshuu leader Katsura Kogorou.