Funny, but then again not surprising, that I find the answer to a childhood question far away, in America, although I was so close (geographically speaking) to the truth. I am living in Rheinfelden, Switzerland, and would be interested in learning more about the meaning and the Oberglatt roots of my name (Oberglatt still is my official 'Heimatort' (home town)).
I'd be grateful, if you could send me the booklet you mentioned. Maybe you have more info on the Rheinfelden/Moehlin - branch of the Derrers ?
I always believed that our name was derived from the demontrative noun 'deren', or similar (meaning "those") - can this hypothesis be positively proven wrong ?