The given name Gimpel is not a nickname (Kinnui) to the Hebrew name
Gimpel or Gumpel is a nickname to Efraim and also to Mordechai.
The source for this names is in Germany in the 15 or 16 century.
The family name Gompertz or Gumperts get out also >from this names.
This names where used in the region what is called 'Nieder Rhein=E2' in
the west part of Germany.