Waza is an event promoted by Heroku, a PaaS company. In Ruby language world there is this tendency to name things after Japanese words (Ruby itself came from Japan, thanks to Matsumoto Yukihiro, a.k.a. Matz), although I have no idea if this influenced Heroku somehow. Heroku itself I don’t think it’s a Japanese word (at least I couldn’t find it in any dictionary I looked at). On the other hand, waza is a Japanese word meanining technique, so it makes perfect sense to name an event focused on technical knowledge after this word.