McCoy, decoy, and coy

Question

A “McCoy” means something that is truly genuine.

The idiomatic expression, “the real McCoy” is used when the speaker wants to emphasize the purity the authenticity of something. It is said to derive from the Scottish McKay (or MacKay) whisky whenever a host offers his guest a drop of the real McKay, whereas the idiom “real mccoy” is said to be an American variant.

Meanwhile, a decoy has quite the opposite meaning, it refers to something or someone who pretends to be something they are not. For example, a designated decoy is, supposedly, a stone-cold sober person leaving a public bar who pretends to act extremely drunk before getting into their car, and driving off. The erratic driving is aimed at drawing the police officers' attention at a sobriety checkpoint, thereby allowing the decoy's inebriated friends to drive home without being caught. (I have no idea how effective this ruse is.)

Finally, coy is just an adjective, and means; acting shy, uncertain, or unwilling to say much, often in order to increase interest in something by keeping back information about it

I was wondering whether all three terms were related or coincidental.

In addition, although the noun coyness exits, the noun coy itself doesn't seem to be listed in any of the online dictionaries I checked, is it an archaic term? If it did exist, what did the noun use to mean?

Answer 1

To me, it is quite obvious that these have separate origins. McCoy refers, as you say, to a name that people have associated a more general term to. So it's not a word in that sense, it's an idiom. Therefore the etymology cannot be compared with the words that make it up.

'Decoy' and 'coy' may be compared more directly. Where 'decoy' come from Dutch, meaning "the cage" (de kooi), the link between the two words are largely unknown, but it is believed that they have influenced each other based on how people have been using them.

Answer 2

I got these from the online Etymology dictionary:

McCoy: as in the real McCoy, 1881, said to be from Scottish the real Mackay (1883), of uncertain origin, though there are many candidates, including whiskey distilled by A. and M. Mackay of Glasgow (the phrase the real McCoy became popular during Prohibition to describe liquor); Charles S. "Kid" McCoy (1872-1940), former welterweight boxing champ; and a claimant for chief of the northern branch of the clan Mackay.

"By jingo! yes; so it will be. It's the 'real McCoy,' as Jim Hicks says. Nobody but a devil can find us there." [James S. Bond, "The Rise and Fall of the Union Club," Yorkville, Canada, 1881]

decoy (n.): 1610s, perhaps from Dutch kooi "cage," used of a pond surrounded by nets, into which wildfowl were lured for capture, from West Germanic *kaiwa, from Latin cavea "cage." The first element is possibly the Dutch definite article de, mistaken in English as part of the word. But decoy, of unknown origin, was the name of a card game popular c. 1550-1650, and this may have influenced the form of the word.

coy (adj.) early 14c., "quiet, modest, demure," from Old French coi, earlier quei "quiet, still, placid, gentle," ultimately from Latin quietus "resting, at rest" (see quiet (n.)). Meaning "shy" emerged late 14c. Meaning "unwilling to commit" is 1961. Related: Coyly; coyness.

One from a Scottish name in the late 1800s, one from the name of a Dutch device (and possibly a card game) in 1600, and one from Old French in 1400. I'd have to say that they're not related, and any similarity in pronunciation is pure coincidence.