If you've been to jiu jitsu competitions, seminars or have been training for a while, chances are that you've heard people say "OSS" around the mats. Maybe you also started saying it out of habit from exposure but have no idea if you are using it correctly. Let’s dive into the history of the term and where it stands today. 

The term “oss” originated in Japan, originally spelled “osu” although pronounced “oss”. There is no question that it is a derivation of a Japanese phrase, however there are a few theories as to which phrase it came from:

1. “Ohayo Gozaimasu”: This means "good morning" in Japanese. Some believe OSS is a shortened version of this greeting.

2. Kyokushin / "Oshi Shinobu": In this style of karate, practitioners use the word as a shortened version of "oshi shinobu". This phrase has several meanings with all of them alluding to perserverence, pushing forward and to endure.

3. "Onegai Shimasu": This term is a greeting used in many Japanese dojos to acknowledge one's training partner before starting a round or request to train together. 

There are arguments from jiu jitsu pracitioners as to which of these theories is best supported. However, most jiu jitsu practitioners today tend to use the term to encourage one another or acknowledge the start of a round together. Given the way it is used in most gyms in America currently, the "onegai shimasu" theory is the most likely origin of OSS.