Aiden is not a made up name. Cayden is variant of Caden. I honestly don't think there is tons of history behind Caden.
From behindthename.com "Sometimes explained as a derivative of the Irish surname Caden, which is a reduced form of the Gaelic surname Mac Cadáin meaning "son of Cadán"."
Personally, Cayden or Caden are just not my style. It follows the very popular trend and appears made up. I personally prefer Noah over Cayden.