For those of you who don't know Bills was the fan name for Beerus up till Battle of gods... and I want to know when did that name come about. was it 2012 or 2013?

2013

When the movie came out but before the official sub was released someone got a hold of a Japanese copy, fan subbed it, and put it online. They misheard the name as Bills and put it as that in the sub, and so anyone you saw that fan sub thought it was Bills as well (until the official sub/dub came out that is)

Good times....