From the report of Edgar v. McCutchen, an 1846 Missouri Supreme Court case:
McCutchen sued Edgar for slander. The slanderous charge was carnal knowledge of a mare, and the word “fuck” was used to convey the imputation. After the verdict for the plaintiff, a motion made in arrest of judgment, for the reason that the word used to convey the slander, was unknown to the English language, and was not understood by those to whom it was spoken ….
Because the modesty of our lexicographers restrains them from publishing obscene words, or from giving the obscene signification to words that may be used without conveying any obscenity, it does not follow that they are not English words, and not understood by those who hear them; or that chaste words may not be applied so as to be understood in an obscene sense by every one who hears them.
Makes sense to me.