I am trying to find the origin / meaning of the phrase "oh musha, musha." I've searched the internet and various books on the origins of phrase and fable to no avail.

The two instances in which I have heard the phrase are: in the movie "Mary Poppins" - the fox says it while being chased by the hunters among whom Mary, Jane and Michael are riding horses from the merry-go-round. Secondly, it was in "The Quiet Man" - said by one of the spectators while Sean Thornton is practicing for the Innisfree cup.

Thanks in advance for any enlightenment you can provide!