These are really "words of power," whether intelligible or not. Originally, the name comes from the languages spoken by the "barbarians," those who did not speak Greek when the Greeks thought they had invented civilization. 

In ritual, barbarous words and names don't have to make sense or be understood by the ritualist. Many are derived from Hebrew, ancient Egyptian and Persian; some are based on the Enochian language provided to us by Dr. John Dee. Rather than rational sense, they make emotional sense with the drama. 

There is some evidence—see Patrick Dunn’s book, Magic, Power, Language, Symbol: A Magician's Exploration of Linguistics—that experienced magicians created certain barbarous words without regard to proper language but entirely to have a magical effect.  

Or, rather, the magician spontaneously speaks these words without plan as if derived from or through the sub-conscious mind. It is, perhaps, related to "speaking in tongues" where a person speaks with no awareness of what she is saying.

Suggested Reading:

Dunn, Patrick: Magic, Power, Language, Symbol: A Magician’s Exploration of Linguistics