Mark Hubey asked

> Ok, then there is no problem. It is an accident. But how does one
> get this meaning from "one"? What does *ad- mean?

*Ad- meant "a sense of motion or direction to, or change into". Ad-
una-mentum means "the process of becoming one with, or changing to
become one with God or man". It is only later with Christian usage
that it becomes associated with the process of being forgiven one's
sins.

Hope this helps

Regards

John