Another interesting historical essay from an on-line amateur etymologist:

The earliest examples of the word otherwise are from Scottish, which suggests a Scandinavian origin, perhaps from a word akin to Norw. dial. fukka "copulate," or Swedish dial. focka "copulate, strike, push," and fock "penis." Another theory traces it to M.E. fkye, fike "move restlessly, fidget," which also meant "dally, flirt," and probably is from a general Low Ger. word, cf. M.Du. fokken, Ger. ficken "fuck," earlier "make quick movements to and fro, flick," still earlier "itch, scratch;" the vulgar sense attested from 16c. This would parallel in sense the usual M.E. slang term for "have sexual intercourse," swive, from O.E. swifan "to move lightly over, sweep" (related to swift). Chronology and phonology rule out Shipley's attempt to derive it from M.E. firk "to press hard, beat." As a noun, it dates from 1680. French foutre and Italian fottere look like the Eng. word but are unrelated, derived rather from L. futuere, which is perhaps from PIE base *bhau(t)- "knock, strike off," extended via a figurative use "from the sexual application of violent action" [Shipley; cf. the sexual slang use of bang, etc.]. Popular and Internet derivations from acronyms (and the "pluck yew" fable) are merely ingenious trifling. The O.E. word was hæman, from ham "dwelling, home," with a sense of "take home, co-habit." Fuck was outlawed in print in England (by the Obscene Publications Act, 1857) and the U.S. (by the Comstock Act, 1873). The word may have been shunned in print, but it continued in conversation, especially among soldiers during WWI.
"It became so common that an effective way for the soldier to express this emotion was to omit this word. Thus if a sergeant said, 'Get your ----ing rifles!' it was understood as a matter of routine. But if he said 'Get your rifles!' there was an immediate implication of urgency and danger." [John Brophy, "Songs and Slang of the British Soldier: 1914-1918," pub. 1930]
The legal barriers broke down in the 20th century, with the "Ulysses" decision (U.S., 1933) and "Lady Chatterley's Lover" (U.S., 1959; U.K., 1960). Johnson excluded the word, and fuck wasn't in a single English language dictionary from 1795 to 1965. "The Penguin Dictionary" broke the taboo in the latter year. Houghton Mifflin followed, in 1969, with "The American Heritage Dictionary," but it also published a "Clean Green" edition without the word, to assure itself access to the lucrative public high school market. The abbreviation F (or eff) probably began as euphemistic, but by 1943 it was being used as a cuss word, too. In 1948, the publishers of "The Naked and the Dead" persuaded Norman Mailer to use the euphemism fug instead. When Mailer later was introduced to Dorothy Parker, she greeted him with, "So you're the man who can't spell 'fuck' " [The quip sometimes is attributed to Tallulah Bankhead]. Hemingway used muck in "For whom the Bell Tolls," 1940. The major breakthrough in publication was James Jones' "From Here to Eternity" (1950), with 50 fucks (down from 258 in the original manuscript). Egyptian legal agreements from the 23rd Dynasty (749-21 B.C.E.) frequently include the phrase, "If you do not obey this decree, may a donkey copulate with you!" [Reinhold Aman, "Maledicta," Summer 1977]. Intensive form mother-fucker suggested from 1928; motherfucking is from 1933. Fuck-all "nothing" first recorded 1960. fuck up (v.) "to ruin, spoil, destroy" first attested c.1916. A widespread group of Slavic words (cf. Rus. blud, Pol. blad) can mean both "fornicate" and "make a mistake." Flying fuck originally meant "have sex on horseback" and is first attested c.1800 in broadside ballad "New Feats of Horsemanship."