Your entry on 'Alan' says that the name came to England with Bretons who followed William of Normandy, but is uncertain about what the name means in Breton. I think it's possible that the name is not originally Breton, but is a reference to the Sarmatian (Iranian) tribe known as the Alans, who lived for a time in Gaul, based in Orleans. Most of them moved south, to Spain and into Africa, but surely some stayed behind. I can easily imagine an Alan reaching Brittany from Orleans and the locals, finding his Sarmatian name unpronounceable, calling him 'Alan'. I've found references in a few online works that say flat out that the Sarmatian Alans are the source of the name 'Alan' in Western Europe. The Alans were nomads who rode horses and introduced the idea of hunting on horseback assisted by pack of dogs to Europe. There's a breed of dogs in France and Spain that's still known as the Alano breed today.
Is there any evidence one way or the other on this idea?