Here's an interesting piece sourced from:
http://larrykagan.com/blog/view/Osu-Oss-Oos-Os8/19/2008 category: martial arts
You hear this during almost every class and outside of class when speaking with other karateka. You probably also say it yourself but what does it really mean?
There's much speculation as to it's true origin. However, the most logical explanation in my opinion is that it's a contraction of the Japanese term "Oshi Shinobu". Oshi means pressure and Shinobu means persevere or endure. Combining these two words into a single phrase or contraction results in the translation to endure under pressure.
Oshi Shinobu = Os
hi Shinobu = Osu
Thus, the correct spelling is Osu. It appears to have been brought into the martial arts by Masutatsu (Mas) Oyama, founder of Kyokushinkai and one of Peter Urban's teachers.
Today, in western dojos, we use it to mean yes, alright, good, hello, goodbye, well done! and more. However, it's greatest impact is during an intense workout. You're on the verge of collapse. Your gi is soaked, your eyes are stinging from the salt of your sweat. Your legs or arms are about to give out from under you. Your sensei speaks some words of encouragement or simply yells out the name of your style Goju!. Now your adrenaline kicks in, you get goose-bumps on your arms, you feel the surge of adrenaline throughout your body, your chi has been restored and you yell in reply Osu!
