"a rule or law," Old English canon "rule, law, or decree of the Church," from Old French canon or directly from Late Latin canon "Church law, a rule or doctrine enacted by ecclesiastical authority," in classical Latin, "measuring line, rule," from Greek kanon "any straight rod or bar; rule; standard of excellence," perhaps from kanna "reed" (see cane (n.)).
The Latin word was taken in ecclesiastical use for "decree of the Church." General sense of "a rule or principle" is from late 14c.; that of "standard of judging" is from c. 1600. From c. 1400 as "the Scriptures, the books of the Bible accepted by the Christian church," also extended to secular books of admitted excellence or supremacy. Meaning "catalogue of acknowledged saints" is from 1727. Musical sense "a kind of fugal composition" is from 1590s. Related: Canonicity.
The secular canon, with the word meaning a catalog of approved authors, does not actually begin until the middle of the eighteenth century .... [Harold Bloom, "The Western Canon," 1994].
c. 1400, "artillery piece, mounted gun for throwing projectiles by force of gunpowder," from Anglo-French canon (mid-14c.), Old French canon (14c.), from Italian cannone "large tube, barrel," augmentative of Latin canna "reed, tube" (see cane (n.)). The double -n- spelling to differentiate it from canon is from c. 1800. Cannon fodder (1847) translates German kanonenfutter (compare Shakespeare's food for powder in "I Hen. IV").
"narrow valley between cliffs," 1834, from Mexican Spanish cañon, extended sense of Spanish cañon "a pipe, tube; deep hollow, gorge," augmentative of cano "a tube," from Latin canna "reed" (see cane (n.)). But earlier spelling callon (1560s) might suggest a source in calle "street."
This use of the word cañon is peculiar to the United States, it being rare in Mexico, and not at all known in Spain or in Spanish South America. [Century Dictionary]
Middle High Indian dialect used in sacred Buddhist writings (the lingua franca of northern India from c. 6c. B.C.E.-2c. B.C.E.), 1690s, from Sanskrit Pali, from pali bhasa "language of the canonical books," from pali "line; canon" + bhasa "language."
Latinized form of name of Mikolaj Koppernigk (1473-1543), Prussian Polish physician and canon of the cathedral of Frauenburg who promulgated the theory that the Earth and the planets revolve about the sun. His great work was "De Revolutionibus Orbium Coelestium." Related: Copernican (1660s).