NOT A HIP HOORAY

The phrase hip, hip, hooray emerged in English in the late eighteenth and early nineteenth centuries as an exclamation for making a toast. Hooray comes from hurrah, which has, along with huzzah, long been a battle-cry used by European armies with no specific definition. Hip is a bit more interesting. Historically, it's been attested as an interjection used to get someone's attention, and it's unclear to what extent that influenced the duplication. A major theory is that it could be related to hep, hep, which was a traditional anti-Semitic rallying cry popularized through the Hep-Hep riots in Germany, where many Jews were killed and their property damaged. There are many fake etymologies swirling around the internet about this one, but it most likely comes from a herding call for shepherds in the area.