hip hip hooray

Recorded as far back as 1803. The word hip was in use then as a meaningless syllable to solicit someone's attention. Hooray (or hurrah) traces back to 1686, and also had no specific meaning, used instead to solicit a person's attention. A folk etymology for this interjection suggests it comes from the anti-Semitic German Hep-Hep riots in 1819, however many examples of Hip Hip exist in English prior to 1819, for example:

1813, Edmond Temple, The Life of Pill Garlick‎[1], London, page 243:The first toast “Success to Pill Garlick lick and his saucy crew,” was drank with nine times nine, hip! hip! hip! and a hoorra! The tumult was excessive.