Washburne
Protector of the key.
Like many Swedish traditions the why is less important that the how. Yep. We don't care much why we celebrate things, as long as you do it right.
To be perfectly honest lots of people just like an excuse to getting really, really drunk. Personally I've never seen the appeal of either forget what happened or becoming sick which many seem to look at as proof that you've had a good time. Each to their own I guess.