well in my search i came up on these 2 explainations:

1) The Milky Way is a translation of the Latin Via Lactea, which in turn is derived from Greek (Galaxias) sometimes referred to simply as "the Galaxy".

2) "The Ganga of the sky", is the ancient Hindu name for the galaxy as viewed from the Earth. this was called "Akash Ganga ", it is the Hindi name for Milky way.

hope that helps....