Where did you find this name before you gave it to your son?
If this is not simply a respelling of
Aaron, then it would be from the Scottish place name, the name of a large island off the southwest coast of Scotland. According to
Adrian Room's
Dictionary of Place Names in the British Isles, it is not known for sure what the name of the island of Arran originally meant, but it might be derived from an ancient Gaelic word meaning "height."