One of the main characters, Hajime Saitoh, was a real person. Saitoh was a swordsman for the Shinsen Gumi throughout the last days of the Bakufu (Shogunate) government and the fighting leading up to the Meiji Restoration. After the defeat of the Shogunate, he did obtain a job in a provincial police organization, where he spent his days before this death near the end of the century.
The television series is based on the manga of the same name but the plot eventually takes off in its own direction.
"Rurouni", translated as "wanderer", is not in fact a real Japanese word. It is a neologism by the original creator of the comic this series was derived from.
Another real-life personality in the show is Toshimichi Okubo. Okubo was one of the men who overthrew the Tokugawa Shogunate, and was one of the founding members of the new Meiji government.
Megumi and Kaoru have the nicknames Kitsune (Fox) and Tanuki (Racoon Dog). In Japanese folklore, the Kitsune and Tanuki are thought of as "dangerous spirits". The Kitsune is said to often take on the form of a bewitching woman who seduces and tricks unworthy men, whilst protecting and rewarding deserving people. These are the two very different attitudes Megumi holds towards Sanosuke and Kenshin. The Tanuki, on the other hand, is said to also take on the form of a woman, but is regarded as much more playful and mischievous than the judgmental Kitsune.