...I thought the true meaning of flak(Flugzeugabwehrkanone) was long, but these examples of other deutsche acronyms is outstanding. :-o
Well, we Germans apparently love to put words together to make new ones, so long words aren't uncommon in German. Many words in German consist of smaller words. But to show that we mean a specific thing and not a combination of others we don't put spaces in there.
Flugzeugabwehrkanone, well, it consists of "Flugzeug", "Abwehr" and "Kanone". Translated it would mean something along the lines of "Airplane defense cannon". So basically we just leave away the spaces. The word "Flugzeug" itself consists of two smaller parts: "Flug" and "Zeug". "Zeug" nowadays is used similarly to "stuff", but it used to mean "something" or even "machine". "Flug" means "flight". So a "Flugzeug" is basically a "flying machine". So a Flak is a "cannon for the defense against flying machines".
That's how all the "Werfer"-jokes wzrk by the way. Many of them are grammatically wrong, but the words still do make a bit of sense. Stuff like "This is a Nebelwerfer, it werfs Nebel" takes apart the word "Nebelwerfer" into the parts "Nebel"/"fog" and "Werfer"/"thrower". Same goes for Flammenwerfer and such.
There's also another way to combine words in German. People familiar with other languages will know about cases of words. As in like there are differents forms for each verb (first, second and third person in singular and plural) there are different forms of each noun for different uses. In English only the pronouns change. In German, mostly only the articles change. Articles are important in German. We have "Der", "Die" and "Das" for masculine, feminine and neutral words. And the grammatical Genus doesn't correlate with the actual item. For example "Chair"/"Stuhl" is masculine, even though it's an item.
Example: "chair" (Damn, it's difficult to think of example sentences)
The chair is standing here. - Der Stuhl steht hier. (nominative)
I put the chair over here. - Ich stelle den Stuhl hier drüben hin. (accusative)
The chair leg (actually I will translate it as "the chair's leg") is broken. - Des Stuhles Bein ist gebrochen. (genitive)
I don't trust the chair. - Ich traue dem Stuhl nicht. (dative)
Same for feminine articles: die, die, der, der
and for neutral articles: das, das, des, dem
(sidenote: most Germans who are familiar with english don't have any trouble with the question of "who" vs. "whom". We are used to determining the case with questions. If you can ask for it with "who (does it)?"/"wer?" it's nominative, if you can ask for it with "who (is it doing something to)?"/"wen?" it's accusative, if you can ask to it with "whose?"/"wessen?" it's genitive, and if you can ask for it with "whom?"/"wem?", then it's dative. So if we use "whom", just by instinct, we normally get it right.)
The genitive is actually becoming rarer and rarer. Just like you wouldn't say "the chair's leg" you wouldn't say "Des Stuhles Bein", but rather "Stuhlbein", which is another noun in nominative. So that's how long words get created. Also how you can avoid the genitive. In many other cases it has now become common to replace genitive with dative, often with "of"/"von", at least in casual, verbal language. Actually you can even pull the m at the end of the dative article "dem" into the pronoun so out of "von dem" becomes "vom".
If there's anybody who is not a native speaker in German, who managed to follow what I was saying please tell me. I would be surprised. Especially due to my tiredness, which always makes me believe I'm just randomly babbling about stuff.