There were a few debated possibilities from where hip/hep came from.  One was from some guy named Joe Hep, who I guess was cool.  One was from opium smokers, who apparently had a saying “on the hip”.  One the words hipi or hipicat, which are from Africa and refer to awareness.

There’s a story for where hip hip hurrah came from that’s supposedly without proof, but evidently spread around regardless.  The story was that hip came from words that meant Jerusalem is destroyed and hurrah meant paradise, so hip hip hurrah would have meant Jerusalem is being destroyed for paradise, roughly.  That would be quite a morbid way to express happiness.