Cannon

Borrowed around 1400 from Old French canon, from Italian cannone, from Latin canna.

This spelling was not fixed until about 1800.

Barnhart, Robert K.; Editor. The Barnhart Concise Dictionary of Etymology. 1995 HarperResource/HarperCollins P.102.

Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002. http://unabridged.merriam-webster.com (December 26, 2006).

Full definition of cannon

(plural cannon or cannons)

A complete assembly, consisting of an artillery tube and a breech mechanism, firing mechanism or base cap, which is a component of a gun, howitzer or mortar. It may include muzzle appendages.(JP 1-02 Department of Defense Dictionary of Military and Associated Terms).
A large-bore machine gun.
A bone of a horse's leg, between the fetlock joint and the knee or hock.
(historical) A large muzzle-loading artillery piece.
(sports, billiards, snooker, pool) A carom.In English billiards, a cannon is when one's cue ball strikes the other player's cue ball and the red ball on the same shot; and it is worth two points.
(baseball, figuratively, informal) The arm of a player that can throw well.He's got a cannon out in right.
(engineering) A hollow cylindrical piece carried by a revolving shaft, on which it may, however, revolve independently.
(printing) Alternative form of canon (a large size of type)

The unchanged plural is preferred in Great Britain and Ireland, while North Americans tend to use the regular plural cannons.

To bombard with cannons
(sports, billiards, snooker, pool) To play the carom billiard shot. To strike two balls with the cue ballThe white cannoned off the red onto the pink.
To fire something, especially spherical, rapidly.

2011, September 2, , Wales 2-1 Montenegro, Montenegro had hardly threatened in the second period but served notice they were still potent as Nikola Vukcevic took a smart pass from Jovetic and cannoned a shot off Hennessey's shins.