[Editor's note: OEN is one of few places left on the web where the word is not censored but is Bowdlerized to "f*ck". Note that in the text below, the algorithm has substituted "f*cking", but "fucken" is left alone, presumably because it is so rarely used any more that authors of the censorship algorithm didn't think to include it.
The word Dick is permitted when it refers to Dick Cheney, though he is arguably an obscene individual; but when D*ck appears it is presumed to refer not to a swimming bird but to a penis.
If you are not familiar with Bowdler, you might be interested to google the history. He produced Victorian editions of Shakespeare that were modified so as not to corrupt young minds.]
During World War II, Revolite developed an adhesive tape made from a rubber-based adhesive applied to a durable duck cloth backing. This tape resisted water and was used as sealing tape on some ammunition cases during that period. The name "duck tape" came both from the backing and from the waterproof qualities, associated with duck feathers.
Years later, duck tape became cheap and readily available, and it found hundreds of uses, among them sealing of ventilation ducts. Somewhere, someone assumed that "duck" was just a product of lazy diction, a bastardization of "duct tape" which must be its true name. Today, both terms are seen in print, but "duct" predominates about 7:1 over "duck".
At least since the Victorian era, "f*ck" was regarded as the most profane word in the English language, and was avoided in print and broadcast media, in public speech, and universally in well-bred society. Usage was confined to alienated outcast subcultures and the underclasses. The adjective "fucken" was inherited from the Olde English past participle, and its traditional connotation suggested degradation and subjugation. Many traditional insults in the English language degrade a man by implying that he is like a woman, and in that tradition, "fucken" meant "subjugated", in the way that a man subjugates a woman.
But with the hippie movement beginning in the 1960s, standards of dress and behavior became more relaxed, taboos against sex and drugs were broken. The word "fucken" crept from the gutter into the respectable student classes. In the process, people mistook fucken for fuckin', as in a slurred pronunciation of the present participle, dropping the last letter. People of the respectable classes unwittingly displayed their ignorance by enunciating the "g" for emphasis, flaunting the fact that "I'm not of the uneducated underclass, but I'm using this word to show how strongly I feel." Today, "f*cking" has displaced "fucken" almost completely among whites, less so among blacks.
In parallel, Western culture was changing. It's no longer OK to be the oppressor, and to be the oppressed is not an insult. (This situation was described a hundred years earlier by Nietzsche  before the transition was consummated, so to speak.) By today's standards of political correctness, it is not cool to call someone a "f*ggot" or a "sissy", but it is an insult to call someone a bully or an oppressor or a male chauvinist pig. Hence it is fortuitously appropriate that with the transition from fucken to f*cking, the insulted person is no longer the fuckee, but the f*cker.
(This essay was inspired by an incidence I read last night of a historical novel, accurate in many other respects, but in which the word "f*cking" was quoted in dialog of a colored person of 1945. It was an anachronism. The word "f*cking" came into the American lexicon only 25 years later.) This history has largely been forgotten, written over and misunderstood.
If it ain't broke, don't fix it
In computer code, there is always a brute-force way to accomplish some logical task, thinking of the rules and the exceptions and the exceptions to the exceptions and writing them all out in gory detail. Then there's the elegant way, when you have a stroke of insight that you don't really need this tangle of if's and else's because there's there's an overarching, clean way to state all these cases with a single line of code. A programmer who inherits someone else's legacy code-or revises his own-is always tempted to replace the former with the latter. We say to ourselves, "it will run faster", but over the years the hardware has become so many millions of times faster that this can hardly matter. "It takes up less space" - yes, that it does, but computer memory has also become a million times cheaper than it wss in 1990. In the end, we do it because we can, because we're proud of our work, and we want it to look elegant to Posterity, or to the next programmer assigned to spelunk through this maze of legacy code.
But the old, inelegant logic has the advantage that it has been used for 30 years, and it works, and we don't really know all the ways that other code has adapted to its inelegance, and whether doing it the "right way" will cause new problems, when doing it the wrong way was causing none. There is also the human psychological tendency to trust our present thinking, to trust that we are now seeing the situation more clearly than we did in the past. In reality, it may be just as likely that my thinking is fuzzy today as that it was fuzzy ten years ago.
"f*ck-a-duck" came into the vocabulary only in recent decades, as an acknowledgment that "f*ck" is no longer taboo, no longer even to be reserved for expression of extreme emotions, but could be playfully and casually deployed in common speech. The phrase means roughly the same as "I'll be gosh darned," and is traceable to the following variant on the nursery rhyme, "Row, row your boat":
f*ck, f*ck, f*ck a duck.
Screw a kangaroo.
69 a porcupine.
Orgy at the zoo.
By the way: "Kangaroo" is the 13th sign of the Zodiac, as reported by the American Urban Dictionary.