The Wicked Witch of the West's name was Elphaba: 

It is derived from the name of the author of "The Wizard of OZ:


L. F(rank) B(aum), L-F-B = Elphaba)

She was also named:

Momba, in the 1925 "Larry Semon in the Wizard of Oz" movie in 1910

Baum never mentions her name...