Surprisingly the OP, Alan Carmack, is not beyond answering historical questions himself, and especially if they are contained in a Shakespearian play. In fact, very recently the OP provided a very good answer to the question
What does "honorable parts" mean?
The expression "honourable parts" is taken from a line in Romeo and Juliet's tragedy
Day, night, month, year! My constant care has been to have my only child worthily matched. And here I find an educated man of equal birth with honorable parts, with fine estates and handsome to behold, and what is my reward?
which is an adaption of the original text, and also cited in the answer
A gentleman of noble parentage,
Of fair demesnes, youthful, and nobly ligned,
Stuffed, as they say, with honourable parts,
Proportioned as one's thought would wish a man;
And then to have a wretched puling fool,
A whining mammet, in her fortune's tender,
Alan Carmack explained that
It is an archaic or rare usage, he continued by citing the OED and we learned about its following entry: “5. archaic Abilities.” which hints at a somewhat historical usage. My question, which prompted the OP's request, was also prompted by a line from William Shakespeare play, Macbeth. It was deemed off topic, so much so, I modified the question until it complied with the frequently cited "Help Centre".
Recently, Alan Carmack and four other users, no doubt persuaded by his acerbic comment left at the bottom of my question, closed a question of mine which I had the audacity and temerity to tag☺—wait for it—etymology.
McCoy, decoy, and coy (visible to users with 10K)
I decided to delete the question, despite it being reopened by a mod, because it was a real pain having to defend it against another user who criticised my free choice and not prohibited by any Stack Exchange rule, to explain why the question was on topic in an edit.
This is a Q&A site, not a forum, chat, general education site, place to list facts, or place to "show off." So unless there is a clear, focused, specific question not answerable with simple Google searches (which is what I did), it's not appropriate even if it's funny, entertaining, informative, or beneficial. Meta is for "questions about questions" and you should have asked this there. Moderators do pay attention to that even if the general audience only rarely goes in there. @LawrenceC
Apparently, I was "showing off". Good to know. Is that why two users downvoted a question that was asking if the noun form coy ever existed? Is that why a user deleted his answer? Perhaps, he didn't want to be tainted with the same tar brush.
The question was:
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 used to mean?
If I had had access to the OED, I would not have asked my question in the first place. Please note that the terms McCoy, decoy and coy (ADJ) are not obsolete, archaic, or even considered rare in the English language.
I would; therefore, strongly suggest that Mr Carmack, and the other user who also voted to close my question but within days posted an answer that consisted solely of citations from etymonline, take a good long hard look in the mirror and see the planks of wood that are wedged firmly in their eyes before pointing out the speck of sawdust in my questions, and in other users' posts that do not conform to their view or hoity-toity judgements.
P.S. FYI I did not downvote any of Alan Carmacks' three answers yesterday. Perhaps the mods could look into the matter.
P.S.S. Am I allowed to post questions that delve into the past meanings of a term? Am I allowed to answer similar questions in the future, without someone telling me that I can't?