canard

I heard a TV newscaster say that there is a group of Republicans who "have bought into Trump’s canard that the election was stolen from him." I have heard that word before and assumed it meant a hoax. My wife, a French speaker, said that the word canard in French means "duck." What's the connection?

She looked in one of her dictionaries and found a 16th-century French expression - vendre des canards à moitié. It literally means "to half-sell ducks" but this was possibly a proverb meaning "to fool" or "to cheat." The origin story isn't known but may have come from someone trying to cheat a customer in the sale of a duck at a market. Can you pass off half a duck as a whole duck and so half-sell it? We don't know. 

English speakers adopted this hoax or fabrication meaning of canard in the mid-1800s. 

There is also an aeronautical use of canard which has nothing to do with a hoax. In aeronautics, a canard is an arrangement wherein a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft or a weapon. 

XB-70 Valkyrie experimental bomber

The term "canard" may be used to describe the aircraft itself, the wing configuration, or the foreplane. You find canard wings used in guided missiles and smart bombs.

This use of "canard" arose from the appearance of an aircraft called the Santos-Dumont 14-bis of 1906, which was thought to look like a duck with its neck stretched out in flight.

1906 Santos-Dumont 14-bis  CC BY-SA 3.0, Link