[yorwba]

"Das Mädchen" is actually neuter, because it's descended from the diminutive of "Magd" (English "maid"). It's the same for "das Jüngelchen", except that "der Junge" is much more common for boys.

I don't think there's any case where German has a word of the opposite gender for a person whose gender is known, because it's usually easy to adapt the default (masculine) form by appending "-in".

[lobster_johnson]

I meant neuter! I studied German for three years in school, but my brain got its wires crossed there for a second.

[rowaway93]

I have a hunch that the nominally feminine gender is rather one of subjunction, not to say subjugation. Der Himmel -> Die Sonne -> Das Wetter. Der Tag -> Die Nacht -> Das Jahr. Der Mond -> Die Sterne -> Das Pantheon ... OK, I am not quite sure, but at least gender was an innovation in Germanic, whereas the reconstructed Proto-Indo-European knew inflection for in-/animate -- e.g. there were two different words for fire, where the the other gave ignition [1].

It stands to reason that the feminin came to be at the boundary between these.

[1] https://en.wiktionary.org/wiki/Reconstruction:Proto-Indo-Eur...

PS: This is fun ... Der Mensch -> Die Familie -> Das Dorf. Der Krieger, die Krieger, das Kriegen. Der Aktionär -> die Aktie. Die Aktionärinnen ... das Aktienpaket. Der Karren (car), Die Karre (load), das Ankarren, das Herangekarrte, das Karree (See [2] for more on four wheels, strange animism, etc. Ultimately inconclusive).

Note that the pluralizing morpheme -en was written -in in old german. Also note that many case inflections come out as -en, so I suppose that female forms were in the objectified part of speech more often, where the gender is not reflected in the article (den Kindern, Männern, Frauen).

[2] http://langevo.blogspot.de/2014/09/four-map.html