In ancient Hebrewthe word abracadabra means "hurl your thunderbold even unto death" and is associated with a thunderbolt diety who perished by throwing himself on the planet so that the creatures of earth could live.
Other scholars feel that the Hebrew interpretation of the word should be ab (father), ben (son), and ruach acadosch (holy spirit).
There is also the debate that the word is Chaldean in origin and not part of cabalistic intrepetation at all. Regardless, we know two things: the diety associated with this charm is male in origin and the word first occurs in the writings of Severus Sammonicus a gnostic physician of the second century.
A really nice in depth discussion of the meaning of the word abracadabra can be found at World Wide Words. Go check it out.