Curious Historical Facts:

SHIT

"In the 16th and 17th centuries, everything has to be transported by ship and it was also before commercial fertilizer's invention, so large shipments of manure were common. It was shipped dry, because in dry form it weighed a lot less than when wet, but once water (at sea) hits it, not only does it become heavier, but the process of fermentation begins again, of which a by-product is methane gas. As the stuff was stowed below decks in bundles you can see what would (and did) happen. Methane began to build up below decks and the if someone came below at night with a lantern, BOOOOOM!Several ships were destroyed in this manner before it was determined just what was happening. After that, the bundles of manure were always stamped with the term (Ship High In Transit) on them, which meant for the sailors to stow it high enough off the lower decks. Thus evolved the term "S.H.I.T." (Ship High In Transit) which has come down through the centuries and is in use to this very day.

FUCK

Even though the acronymic explanations for words such as SHIT, FUCK etc. are indeed interesting and catch our fancy, they are rarely true. FUCK neither stands for:

Fornication Under Consent of the King
Fornication Under Charles the King
Fornication Under Crown of the King
Fornication under Christ, King
Forbidden Under Charter of the King (a sign posted on brothels closed by the Crown)
For Unlawful Carnal Knowledge
Forced Unlawful Carnal Knowledge
File Under Carnal Knowledge (how Scotland Yard marked rape files)or others as widely suggested.

The real origin is by far more tedious...

quote[Fuck] was first recorded in English in the 15th century (few acronyms predate the 20th century), with cognates in other Germanic languages. The Random House Historical Dictionary of American Slang (Random House, 1994, ISBN 0-394-54427-7) cites Middle Dutch fokken = "to thrust, copulate with"; Norwegian dialect fukka = "to copulate"; and Swedish dialect focka = "to strike, push, copulate" and fock = "penis". Although German ficken may enter the picture somehow, it is problematic in having e-grade, or umlaut, where all the others have o-grade or zero-grade of the vowel. AHD1, following Pokorny, derived "feud", "fey", "fickle", "foe", and "fuck" from an Indo-European root peig2 = "hostile"; but AHD2 and AHD3 have dropped this connection for "fuck" and give no pre-Germanic etymon for it. Eric Partridge, in the 7th edition of Dictionary of Slang and Unconventional English (Macmillan, 1970), said that "fuck" "almost certainly" comes from the Indo-European root *peuk- = "to prick" (which is the source of the English words "compunction",
"expunge", "impugn", "poignant", "point", "pounce", "pugilist", "punctuate", "puncture", "pungent", and "pygmy"). Robert Claiborne, in The Roots of English: A Reader's Handbook of Word Origin (Times, 1989) agrees that this is "probably" the etymon. Problems with such theories include a distribution that suggests a North-Sea Germanic areal form rather than an inherited one; the murkiness of the phonetic relations; and the fact that no alleged cognate outside Germanic has sexual connotations.