1660s, "arouse by knocking at the door," from knock (v.) + up (adv.). However it is little used in this sense in American English, where the phrase means "get a woman pregnant" (1813), possibly ultimately from knock in a sense "to copulate with" (1590s; compare slang knocking-shop "brothel," 1860).
Knocked up in the United States, amongst females, the phrase is equivalent to being enciente, so that Englishmen often unconsciously commit themselves when amongst our Yankee cousins. [John Camden Hotten, "The Slang Dictionary," London, 1860]
also chode, "penis," by 1968 (Zap Comix), U.S. teen slang, of unknown origin. Guesses include supposed Navajo chodis "penis" ["Cassell's Dictionary of Slang" 2005], or a supposed Hindi, Bengali or Gujarati vernacular word for "copulate" ["New Hacker's Dictionary," 1996].
late Old English horsian "to provide with a horse or horses," from horse (n.). Related: Horsed; horsing. Sense of "to play excessive jokes on" is by 1893, mostly in formation horse around (1928), perhaps from horse-play, or from earlier nautical jargon use of the verb in reference to men, "drive or urge to work unfairly and tyrannically" (1867). But also consider the vulgar expressions arsing about (1660s), arsing around (1922).
[A] favorite pastime for many men is to "horse" or guy a friend who has shown himself susceptible to ridicule or fun making. "Horsing" is extremely wholesome mental discipline for over sensitive or super-conceited young men. "Horsing" always implies a joke at another's expense. As to how it came into use there is no satisfactory theory to offer. [Yale Literary Magazine, December 1893]
As a verb, horse also meant "to mount on horseback" (early 14c., horsen), "to spank" as one does a horse to get it to go (1825), also "to copulate, mount" (as a stallion does a mare), hence figuratively, of men, "copulate with" a woman (mid-15c.).
mid-15c., ramblen, "to wander, roam about in a leisurely manner," perhaps frequentative of romen "to walk, go" (see roam), perhaps via romblen (late 14c.) "to ramble." The vowel change is perhaps by influence of Middle Dutch rammelen, a derivative of rammen "copulate," "used of the night wanderings of the amorous cat" [Weekley], or the Middle English word might be from the Dutch one. Meaning "to talk or write incoherently" is from 1630s. Related: Rambled; rambling.
early 15c., "to copulate" (of wolves, dogs), literally "to range (things) in a line," from Old French alignier "set, lay in line" (Modern French aligner), from à "to" (see ad-) + lignier "to line," from Latin lineare "reduce to a straight line," from linea (see line (n.)). Transitive or reflexive sense of "to fall into line" is from 1853. International political sense is attested from 1934. The French spelling with -g- is unetymological, and aline was an early form in English. Related: Aligned; aligning.
"copulate with," 1788 (Grose), probably from obsolete verb shag (Middle English shoggen, shaggen, late 14c.) "to shake, waggle," which is of obscure origin but probably related to or an alteration of shake (v.):
And þe boot, amydde þe water, was shaggid. [Wycliffite sermon, c. 1425]
Compare shag (v.), used from 1610s in a sense "to roughen or make shaggy," from the noun shag. Also compare shake it in U.S. blues slang from 1920s, ostensibly with reference to dancing. It also was the name of a dance popular in U.S. in the 1930s and '40s. Related: Shagged; shagging.
Related Middle English swive was the principal slang verb for "to have sexual intercourse with," a sense that developed c. 1300. This probably explains why, though the root is verbal, the verb swivel is not attested in Modern English until 1794. Compare Middle English phrase smal-swivinge men "men who copulate infrequently."