Suhm, surnommé le Diaphane"

That's fascinating, and definitely predates any other use of the nickname I've seen so far. This argues he did indeed choose it for himself, though I suppose it's possible 16 years old Fritz after Suhm consoled him during the Hubertus Hunting disaster or thereabouts could have come up with it, but I think it's more likely Suhm himself did. (Makes sense. Would you want to be known forever as "Little Devil" ?)

Du Bourgé: search me, I've got no idea. The English envoy - wasn't Hotham yet, I think Hotham arrived in early 1730, so Guy Dickens? Anyway, poor Suhm indeed. In a way, it's a minor miracle that he lasted as long as he did in Berlin. All the other examples of when an envoy was seriously disliked/distrusted by the ruling monarch resulted in the envoy being withdrawn and replaced pretty soon - see Charles Hanbury Williams. (Or younger Manteuffel himself, the moment he went from getting results in Denmark to pissing off the King.) I mean, being an envoy isn't a popularity contest, and you can win a King around enough to work with him - Valory evidently managed to do that with Fritz, and Manteuffel went from being suspected of being part of a complicated murder/coup d'etat plot by FW to being buddies again eventually - , but Suhm almost got strangled, and that would be usually the point where it's time to cut your losses and send another guy. It occurs to me that if the almost strangling happened in 1727, and Flemming died in 1728, then the reason why Suhm wasn't replaced in 1727 already might simply have been because Flemming was too sick to be up to an ambassadorial reshuffling, and then in 1728 after he died, there was a big reshuffling anyway.