Yes, seeing as the first three U-boat Pour le Merites all went to Ottos...Weddigen, Hersing, Steinbrinck (Walther Forstmann broke the trend as #4 in late 1916), and I know there was at least one more PLM'd Otto (Wuensche). Pat and I sometimes just call them "Otto Three" or the sort as a joke, since there were so many with PLMs, and even more without. Then you get WWII with Kretschmer, et. al., which just makes it worse!

As for the Otto Schwieger thing, that did strike me as odd, since I believe his full name was Walther Kurt von Schwieger, so it couldn't even be referring to him by his middle name.

I don't know that the "silent" part comes in, since that's associated with "Silent Otto" Kretschmer of WWII, and by all accounts Schwieger was actually a pretty jovial man (both Werner Fuerbringer, his first officer, and Rudolf Zentner, his second officer, make ready mention of him being a nice, warm-hearted guy to his crew).

My guess, if it was a nickname in the U-boats, was to associate "Otto" with a successful commander, in light of the successes of Weddigen, Hersing, and Steinbrinck. After all, they did nickname the medal the "Blue Max", so I suppose giving a good captain the mark of nicknaming him "Otto" wouldn't be too much of a stretch.