Old English cnotta "intertwining of ropes, cords, etc.," from Proto-Germanic *knuttan- (source also of Low German knütte, Old Frisian knotta "knot," Dutch knot, Old High German knoto, German Knoten, perhaps also Old Norse knutr "knot, knob"). For pronunciation, see kn-.
Figurative sense of "difficult problem, a perplexity" was in Old English (compare Gordian knot). Symbolic of the bond of wedlock from early 13c. As an ornament of dress, first attested c. 1400. Meaning "thickened part or protuberance on tissue of a plant" is from late 14c. As "small group or cluster of persons" late 14c.
The nautical unit of measure of speed (1630s) is from the practice of attaching knotted string to the log line at equal distances (see log (n.2)). The ship's speed can be measured by the number of knots that play out while the sand glass is running.
The distance between the knots on the log-line should contain 1/120 of a mile, supposing the glass to run exactly half a minute. [Jorge Juan and Antonio de Ulloa, "A Voyage to South America" 1760]
Hence the word knot came also to be used as the equivalent of a nautical mile (in pre-World War II use in U.S. and Britain, about 6,080 feet). A speed of 10 knots will cover ten nautical miles in an hour (equivalent to a land speed of about 11.5 mph).
c. 1300, marien, of parents or superiors, "to give (offspring) in marriage," also intransitive, "to enter into the conjugal state, take a husband or wife," from Old French marier "to get married; to marry off, give in marriage; to bring together in marriage," from Latin marītāre "to wed, marry, give in marriage" (source of Italian maritare, Spanish and Portuguese maridar), from marītus (n.) "married man, husband," which is of uncertain origin.
Perhaps ultimately "provided with a *mari," a young woman, from PIE *mari-, *mori- "young wife, young woman" (source also of Welsh morwyn "girl, maiden," Middle Welsh merch "daughter"), akin to *meryo- "young man" (source of Sanskrit marya- "young man, suitor").
By early 14c. as "to take (someone) in marriage, take for a husband or wife;" by late 14c. as "become husband and wife according to law or custom; get married (to one another)." Transitive sense, of a priest, etc., who performs the rite of marriage, "to unite in wedlock or matrimony," by 1520s.
Figurative meaning "unite intimately or by some close bond of connection" is from early 15c. Related: Married; marrying. Phrase the marrying kind, describing one inclined toward marriage and almost always used with a negative, is attested by 1824, probably short for marrying kind of men, which is from a popular 1756 essay by Chesterfield.
In some Indo-European languages there were distinct "marry" verbs for men and women, though some of these have become generalized. Compare Latin ducere uxorem (of men), literally "to lead a wife;" nubere (of women), perhaps originally "to veil" [Buck]. Also compare Old Norse kvangask (of men) from kvan "wife" (see quean), so, "take a wife;" giptask (of women), from gipta, a specialized use of "to give" (see gift (n.)), so, "to be given."