Meaning

noun a large artillery gun that is usually on wheels

noun heavy gun fired from a tank

noun (Middle Ages) a cylindrical piece of armor plate to protect the arm

originAttested from around 1400 as Middle English canon, canoun, from Old French canon, from Italian cannone, from Latin canna, from Ancient Greek κάννα (kánna, “reed”), from Akkadian 𒄀 (qanû, “reed”), from Sumerian 𒄀𒈾 (gi.na) (for more, see cane). Doublet of canyon. This spelling was not fixed until about 1800.

Etymology from Wiktionary, CC BY-SA 3.0