Iron Klaus, or Tetsu no Klaus

I've always assumed that the nickname "Iron Klaus" is a pun on the English phrase "iron clause". (And for those whose native language is not English, it's a fairly common phrase for a clause in a contract that cannot be broken.) I figured that the phrase was probably about the same in German, as German and English have quite a few cognates, and that Aoike-san had come across it in research and named her hero for the sake of the play on words.
Then yesterday I finally bothered to look up "iron" and "clause" in a German-English dictionary, and discovered that German for "clause" is "Klausel", which is close but a bit of a stretch for the pun, and that "iron" isn't a German word at all; in German it's "Eiserne".
It seemed kind of odd to me that a German character would have a nickname that was a pun in English, so I asked Nico (who is German) about this.

I have certain doubts that Iron Klaus is a pun on that English phrase. In Japanese he is called Tetsu no Klaus, Klaus (made) of iron, and not "Irono Kurausu" (or however they would spell his name), means it isn't an English term to start with, but a Japanese one. This speaks against any pun on an English phrase, but a more general one, which one should be able to understand, no matter which language the manga is in.
I remember (even though I'm not sure where that phrase originally came from) that there is a German phrase describing our soldiers, especially during the second world war (maybe also WWI) as "hart wie Kruppstahl". It's a bit tricky to translate that phrase. "Hard as steele from Krupps" I think would be the best translation. Krupps is nowadays a company selling electric equipment, everything from dish washers to toasters:) During WWII it was (if I am not fully mistaken) also into producing metal as well as (heavy) weaponry, and their steel was said to be the hardest and best produced in Germany at that time. I don't know how old that company is, but it's possible their building weapons reaches back into the last century, especially building heavy canons for whatever war Germany fought in. So the "hart wie Kruppstahl" phrase was somewhat of a compliment to the German soldiers' physique and ability to endure hardships, not easy to break etc.
The other phrase which comes to my mind is "der Eiserne Kanzler" (the Iron Chancellor), the nickname Reichskanzler Otto von Bismarck earned while he was chancellor of Germany (around 1870-1900, not sure about the exact dates a the moment). I imagine him very much like Klaus' father, hard, calculating up to a certain point, no nonsense, proud of Germany and his grand heritage, a brilliant strategist etc.
So I would assume that the "iron" in Iron Klaus is probably based on those two phrases. The pun against the Iron Chancellor might make fun of his behaviour, his aristocratic and somewhat conservative upbringing, so ancient he could have lived in Bismarck's times. The other pun "hart wie Kruppstahl", describing German soldiers during WWII, is probably directed against his physique as well as his temper, the blockheaded German tank:)
I don't think Klaus has anything to do with "clause" at this point. It's simply part of his name. But the "iron" part is a pun against his German heritage, no matter which language you are in, English or Japanese. And no, iron is certainly not a German word. The only German word we have that spells similarly is "ironisch/Ironie" (ironic/irony) ;-)

Anne (former historical linguist)
Actually, "iron" and "eisen/eisern" are cognates coming from the same Germanic and before that Indo-European root. The original Old Englisch was also "isen/isern" and the other Germanic languages also have "s." This change from "s" to "r" is called rhotacism and it occurs quite often in languages. Other examples in English would be "was/were" and "lose/forlorn."

I just want to add that I wouldn't think the "iron=German" reference was intended to make fun of Klaus or Bismarck or anything else, but simply to characterize Klaus. But then, I like Bismarck.

Right, I think it's very likely that the writer, who's acknowledged to be a nut case of the western history, nicknamed the Major inspired by that of Bismarck, though the German politician is rather known as "Iron-Blood Chancellor" among us Japanese. (If I remember correctly, "iron" here signifies industry whereas "blood" means military.) You may have recalled that Klaus is also portrayed as "Prince Iron Blood" in James the Coin King story.

"Blood and iron" was a favorite phrase of Bismarck's. The most famous instance of his using it was when he said, "The great questions of the day will not be settled by speeches and majority decisions, but by blood and iron."
Anyway, kudos to Aoike-san, making a hell of a good pun without even meaning to, in a language she doesn't even speak.

That's true. For instance, the titles of the stories make me wonder if she intended to make them puns or not. The original Japanese title for "Pandastic Maze" (actually it's in Chinese) is, strictly speaking, "A Maze Like Panda," which really doesn't make sense other than that it suggests that the story has something to do with China. But if a person familiar with English language associates "like panda" to "pandastic" to "fantastic," it starts sounding like a pun.

A couple of months later, Masae cited an article by a British author that described a homosexual as "a bit of an iron". A footnote explained that this expression was derived from Cockney rhyming slang, "iron hoof" for "poof" (homosexual). She suggested this might have something to do with why Lawrence sniggers when saying Klaus's nickname. Turns out Aoike-san is even better at unintentional plays on words than we thought.