Meaning

adjective making great mental demands; hard to comprehend or solve or believe

adjective used of old persons or old trees; covered with knobs or knots

adjective highly complex or intricate and occasionally devious; ; ; ; ; ; ; ; - Sir Walter Scott

originFrom Middle English knotti, knotty (“having a knot in it; full of knots; tied together (?); resembling a knot, knotlike; having knobs or protuberances; bulging, convex; of a tree, branch, etc.: full of knots, gnarled; of a plant cutting to be grafted or planted: full of buds or eyes; having joints (?); having swollen joints; of flesh: glandular; of flesh: granular, lumpy, especially, having many…

Etymology from Wiktionary, CC BY-SA 3.0