It seems I managed to find the roots of my last name. There is a Polish city called Kolobrzeg that used to be German: Kolberg/Colberg (in 1891, they changed the C to a K - during World War II, the city gained some notoriety because of a propaganda movie made there). Interestingly enough, the original name Colberg (first mentioned in 1255 or so) apparently is derived from the Polish “kolo brzegu” which means (crudely translated) “city by the banks of the sea”.