ThankQ for that.
Supposedly, the Marines “oohrah” is an outgrowth of a submarine claxon during a dive - “ar-uga”
I started doing a little research on it and found the following interesting little factoid, dating to 1898, before submarines:
Cheerleading’s roots are closely tied to American football’s. The first intercollegiate game was played in 1869, between Princeton University and Rutgers University in New Jersey, and by the 1880s, Princeton had formed an all-male pep club. A graduate of Princeton, Thomas Peebles, took the Princeton cheers to the University of Minnesota, where football and fight songs were becoming very popular. In 1898, U of M was on a losing streak, and a medical student named Johnny Campbell assembled a group to energize the team and the crowd. Johnny picked up a megaphone and rallied the team to victory with the first organized cheer: “Rah, Rah, Rah! Ski-U-Mah! Hoo-Rah! Hoo-Rah! Varsity! Varsity! Minn-e-so-tah! (varsity.com)