Hi Chrisell,
In this case, it is no 'dis'-ending but an 'is'-ending as it is a Latinized form of
Adelheid or Aleid.
There are many Scandinavian names with a 'dis'-ending which look quite similar, but which are not related to Aleydis, e.g. Adis, Agdis, Aldis, Alfdis, Alvdis, Ardis, Arndis,
Asdis.
/
Satu
http://www.nordicnames.de/