Arshaan can be another spelling of Arshan, for its details see this page: Arshan
Arshaan is also the ancient name of a Persian prince. The name means "brave", "courageous", "doer of good deeds". It can also be spelled as Arshan, Ershan, Ershaan, Arsaan. It is pronounced as (U)nde(RS)t(AN)d (or with "sh" instead of "s"). It is not an Islamic name but Muslims may use it since it has a good meaning.