My dear sainted grandmother from County Waterford always said "Musha, musha,musha" when she saw people kissing on tv.

I am now watching the movie Mary Poppins and in the carousel/hunt scene a hunted fox ( who is Irish) says "Oh Musha!" when he notices he is being pursued. After reading all the comments I am thinking that "Musha" means "Well!" or "Indeed!"

p.s. the movie is good as you remember