Dear Nancy and David, 

I do not know Tibetan, but - but, couldn't that mysterious -aja be a continuation of OIA ārya–, added to names/titles in its MIA/NIA forms?

Look, please at my paper:

https://www.academia.edu/8718097/A_Short_Note_on_the_Hindi_Honorificum_-ji_in_Rocznik_Orientalistyczny_T._LX_Z._2_2007_pp._279-282_

Artur Karp
Poland