Well i've got some good news..i found it..:)
I don't know if you're Dutch, but if you are, here's the link:
http://www.meertens.knaw.nl/voornamen/VNB/index.phpNow fill in "Dimmen" in the white box...
As you can see (or not if you're not Dutch) it's a variant of Dimme and perhaps Dingemans. Now Dimme (fill in Dimme in the white box) is a male name (on the site you see many other names that are variants of Dimme, such as Tiemo, Tjomme etc). Dimme is a German name, that originally is made out of 2 parts: the part "diet" (pronounced as Dete / Deet, not Dye-et / Die-et) meaning "Volk" (= Nation, People) and of which the second part started with a M, such as Diet-mar.
So basically you can say Dimmen means "Nation" or "People" (my dictionary gives out 2 meanings, but Nation comes closer i think)
Also, it might be nice to know that Dimmen is also a Verb in Dutch, with 2 meanings: Dim / Dip (as in to make the light less strong, but not switching them off, if you know what i mean?!)
The other meaning of the verb Dimmen is more 'streetlanguage' or ' the popular meaning of the word' Dimmen is often used by moms to tell their kids to shut up, or fight less..also, see light, i think you see the connection?! :)
Well that's it, if there are any questions, let me know!