..is Arnfast (AHRN-fast, the last a is soft, not like in the english word "fast"). It's origin is propably german, and I know it was used as a first name in the Middle Ages.
I am asuming that the Arn-part means "eagle" like the other names starting with Arn (i.e. Arnold). I'm more unsure on the fast-part, but as the modern german word "fast" means "almost", could it be possible that Arnfast means "eagle-like"?