His mother, Ida Elisabeth Hammerich, was the official translator of the
Danish version of the newspaper/magazine cartoon "Peanuts". One of the
characters, the little dirty and dusty boy "Pigpen", was called "Rumle"
in the Danish version. As her own son, Jens Peter, as a kid seemed to
copy the habits of getting dirty and dusty, she nicknamed him Rumle.
And the name, not the dust, stuck.