mid-13c., "full of knots" (figurative use, of questions or problems, is attested from early 13c.), from knot (n.) + -y (2). Related: Knottiness.
Entries linking to knotty
knot n.
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).
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.