-ken is a Low German and Frisian diminutive suffix used to create diminutive forms of names.
Most of the Low German names came to the Nordic countries during the time of the Hanseatic League, a trade group during the 14th - 17th century.
Old variant forms are -gen/-gin/-gina/-kin
Closely related is the High German suffix -chen.
Variant spellings include: -cken, -kken
Creative spelling variants are -chen and -cen, in old documents, you will sometimes find the variant -kin.