It seems that during the big band era, some of the musicians had what they called head arrangements. All of the musicians knew them and could get together and play them, but they weren’t necessarily official songs. One of the songs I had a nickname of blue balls. One night on a radio show Count Basie play the song, and the announcer ask him the name of the song. He knew that he could not say the name on the air, so he looked up at the clock and just called it the 1 o’clock jump. So apparently this may be out this song got its name.