Q From David Nix: I have just discovered your web site and it is immensely enjoyable. I have a word that came to mind, cocksure, and I wonder if you might know of its origin?
A It’s good to hear you like the site. Just for once I can repay a compliment by providing a straightforward answer, though it’s more complicated than it looks.
It seems obvious at first sight that cocksure means “as sure as a cock”, alluding to the arrogantly self-confident strut of a barnyard cockerel. That would fit the form of phrases like coal-black or stone-deaf. The problem is that cocksure has changed what it means down the centuries and the obvious answer doesn’t fit the facts.
Back in the sixteenth century, if you said you were cocksure you meant that you were absolutely safe, free from danger or secure in your position. This example, a late one in this sense, would be misunderstood by us today:
All such persons as shall be nominated by the Parliament, shall be cock-sure in their Authority.
The History of the Wicked Plots and Conspiracies of our Pretended Saints, by Henry Foulis, 1662.
The word evolved via the idea that somebody was trustworthy or reliable, or absolutely certain to do something, to today’s sense of being dogmatically certain in one’s own mind about some matter or of being presumptuously or arrogantly confident.
So where does it really come from? It seems certain that the cock in cocksure is a euphemism for God. This appeared in a variety of medieval oaths down to the time of Shakespeare, including cocks bones, cocks passion, cocks wounds and cocks bodikins. So the original meaning of cocksure was that a person enjoyed a security or quality of rightfulness equivalent to that of God.