If the 1905 book “French Idioms and Proverbs: A Companion to Deshumbert’s ‘Dictionary of Difficulties'” is to be believed, the word originated from some now long-forgotten French anecdote about ‘half-selling a duck’ to someone: “vendre à quequ’un un canard à moitié.”
The original crime would have to be recreated with some imagination: A marketplace. A shady, shifty-eyed con-man. He ostensibly offers a duck for your supper feast held in one hand, takes your ducats with his other hand, then suddenly turns and ducks off into the crowd.
To call someone or something a canard is to call them (or it) a cheat, a swindle, or a lie.
The other utility for this French word is in aeronautical engineering, going back to the dawn of powered flight. Most planes have a horizontal control surface on their tail: a tailplane. A few, though, have these control surfaces near their nose instead. Used to pitch the aircraft up or down, these forward control surfaces are known as canards.
The original 1903 Wright Flyer had canards. The coinage of the term occurred three years later, in 1906, when Brazilian aviation pioneer Alberto Santos-Dumont launched his 14-bis, also dubbed the “oiseau de proie” (“bird of prey”), from the fields of Neuilly-sur-Seine. However, what he saw as a “bird of prey” was seen by others as a “duck”-shaped aircraft, with a long neck and wings in the rear. The observers’ coinage stuck, and thus, a forward control plane has been known as a canard in aeronautical engineering ever since.
In a way, these forward control surfaces, these aeronautical canards, do “cheat.” You see, normally a tailplane has to force the body of an aircraft to pitch up or down. It is not very energy-efficient, though it is easier to control. The forward control surfaces make it very easy to pitch up-or-down. In fact, it can make it too easy.
The Eurofighter Typhoon (pictured at the top of the article) is a modern variant of such aircraft. Its canard design makes the aircraft far easier to pitch than a tailplane design. However it requires computerized controls, known as “fly-by-wire” systems, so that the aircraft doesn’t pitch head-over-tail and tumble out of control.
All of this goes to show that a word in one language may have a literal meaning (“a duck”), yet when it becomes a loan word in another, it can have a multitude of meanings. Whether for technical documentation or for idiomatic prose, you should consider experts on your next translation or localization job. Otherwise, someone might half-sell you a duck!