yes it is confusing but my final conclusion is that Hazelinus and Azelinus aren't necessilary related (probably not at all)
so, Ashlyn and Ascelin have both the same origin ( asc and lin ) and Hazelinus is a variation of Hessel, of which etymology is unclear, but i'm pretty sure that all those surnames like Hazlin, Hessling and Asselink are from Hessel (they all mean 'son of Hessel' i think)
anyway, Ascela is a female form of Ascel and Ascel is from the Germanic word asc (meaning Ash). that's about it.
i'm still waiting for reactions from Meertens Instituut and someone else and i also haven't got the translation yet (of the Slovakian site, but that is not relevant anymore i guess)