About a year ago, in a discussion of "Git Along," evidence was posted from the University of New Mexico site that the song derived from calls of the Spanish-speaking southwestern cowboys. See post of 10 Dec 01: Yippie yi yei yippie yi yo

See "Cowboys - Vaqueros: Origin of the first American Cowboys," by Donald Gilbert Y Chavez. His article is reproduced at the Univ. New Mexico site, Vaqueros
An important summary of western words supplemental to Ramon F. Adams "Western Words" is included.
A fragment-
English- Yippie yi yea yippie yi yo
Spanish- Eppi eh alli, eppi eh yo
Translation- How are things over there? hey eh? hey eh?
and so on- see the thread and the website for the whole.

So- Eppi yi yea, vamos .....!