Question regarding jargon on modern U-boats

[frau kaleun]

"Kaleun" or "Kaleu" in German naval lingo is not specific to the u-boat service... it's actually a verbal abbreviation for "Kapitänleutnant," a German naval rank.

From http://en.wikipedia.org/wiki/Captain_Lieutenant

Kapitänleutnant is the third lowest officer's rank in the German navy. The U.S. Navy's rank of Lieutenant is equal to Kapitänleutnant in NATO's military hierarchy (classed as OF-2). Nevertheless, a Kapitänleutnant may command smaller ships (e.g. submarines class 206A) or serve as Principal Warfare Officer on larger warships, giving the rank responsibilities more along those of a Lieutenant Commander in the U.S or Royal Navies. The abbreviation of the title to "Kaleu" (contemporary usage) is used officially in verbal communication; the commander of the Type VIIC U-boat U-96 in the film "Das Boot" was of this rank, and called "Herr Kaleun" (historical usage) by his crew.

It was a rank commonly held by combat U-boat commanders during WWII and so (around here at least) has become the default "title" for WWII u-boat simmers. In RL though a submarine commander would be addressed that way only if he held that rank, not because he commanded a sub. And if he held the rank he'd be addressed that way whether he was on a sub or not.