In World War Two, “Jody” was the guy back home who was keeping company with your girl. Marching cadences have been around for a long time. I can easily picture a Roman Centurion belting one out to keep the march in line. Since 1945 they’ve been evolving.
Here’s one from the movie “Battleground” from 1949.
From “Full Metal Jacket”- Vietnam
Airborne Rangers- “Army Heard You Callin'”.
You gotta Love the Marine Corps
Here We Go Again
Air Force Female Basic Training Flight 508, 2011.