Yes, Sonder is a word in German which means "special", as in the German term Sonderweg which is the German equivalent of "American Exceptionalism" ("German Exceptionalism", I suppose).
The German "sonder" referred to in this branch of the conversation (i.e. meaning special) is not a word on its own but a prefix for other words [0] (remember that germans like to build words from multiple separate parts and words).
While "sonder" itself is a word, it means something different when used on its own (without) [1].
While "sonder" itself is a word, it means something different when used on its own (without) [1].
0: https://www.duden.de/rechtschreibung/Sonder_ 1: https://www.duden.de/rechtschreibung/sonder