-chen is a High German diminutive suffix used to create diminutive forms of names.
It derives from the Germanic diminutive suffixes -ka/-ko which in Old High German changed to -cha. Then it merged with another Germanic diminutive -īn (see also -lein) and became -chīn/-chin/-chen in Middle High German and -kīn/-kin in Old Saxon (-ken in younger Low German and Frisian).
In the Nordic countries, -chen is sometimes also used as a creative spelling -ken.
A Dutch variant form is -je.