I finally broke the tension with my fellow teachers in the school office today. As I was leaving work, I bowed and said: “Osaki ni shitsurei shimasu”, which is a polite saying used when leaving work for the day. It can be translated as: “I am being rude by leaving before you.”
Very polite, very formal, very Japanese.
Today, however, a fellow teacher told me that I should say: “Osaki ni doron.” I asked what it meant and no one could give me a straight answer as they were all giggling behind their desks. I assumed it was something silly and decided to use it as I left, so I bowed deeply and repeated: “Osaki ni doron”…and the whole room burst into uncontrollable laughter! It was quite the way to make an exit.
Although the teachers at the office wouldn’t tell me what the phrase meant, some new friends of mine told me that it is an old joke, and essentially takes the polite phrase “I am being rude by leaving before you” and turns it into: “I’m outta here like a disappearing Ninja!”