There is an excellent article for ALANS in wikipedia. There are many forms of the name with its origins to the 1st century BC. Coming from a nomadic people on the Eastern step region of the Baltics. (near modern day Georgia near Russia)
Basically, people from this tribe traveled to the north of the mediterranean region, to Gaul/France, Spain/Portugal, to Northern Africa and back. There are some good maps in the article showing the movement.
In addition to this article, I recently met someone with the spelling alanis. The name had a greek origin with a variation on the spelling for Atlantis.