Another story (backed by a few books) states that AUDI is the short of the word AUDIO, which is what the founder's name is in Latin or Greek.

I would rather go for the first explanation rather than the 2nd one, still makes more sense than the 2nd :)

On the topic of Auto Union, the link below might interest one particular Pahang resident, Mr. Heinz, do oblige with a few insights into this particular brand or model please.

Have a good day!