[hndl]

Interesting contrast on the vocabulary. A bit of Googling reveals a possible explanation:

>In the field of religion there are some interesting contrasts. Words such as devá have the meaning of god in the Vedas have the meaning of devil in the Avesta. Likewise some names for Vedic gods show up in the Avesta as evil spirits. This is likely due to the ancestors of the migrants to North India being a competing tribe of the tribe responsible for the creation of the Avesta.

Taken from: http://www.sjsu.edu/faculty/watkins/sanskritavestan.htm