I-ro-ha- The first three letters in the old (defunct) Japanese alphabet, which originally comes from a short song: "Iroha nihoheda chirinuruwa wagaya dareza tsuenarama uyina okuyama kyoukoete asaki yumemiji yohimasezu." If I felt like translating I would have said "the ABC's" and the meaning would come across right down to the nuance as "i-ro-ha" is still used in modern Japanese as slang for the basics of anything...
Hakama- "Pants" like the ones Kenshin is wearing (Ken's kimono-pants that look like a divided skirt. (Walter's Note: Hakama's were originally worn by samurai to disguise their movements. That's why they're long and dress-like so you can't really see the movements of the person's legs.)
Rougai- This is slightly more archaic/herbal medicine why of saying tuberculosis. The more common way to say tuberculosis in Japanese is "kekkaku."
Kohantoki- One "toki" is the old Japanese measure of time and it is 2 hours. "Hantoki" is half that, an hour -- so "kohantoki," a "small hantoki" is half a hantoki -- therefore, half an hour.
