My musings on this word were provoked by coming across neighsayer in a book review in my newspaper. There are numerous examples to be found in the archives of journalism but they’re almost always dreadful sub-editorial headline puns on some horse-related controversy. Not in every case, however. A minority — like the one I spotted — demonstrate that their writers have lost the etymological plot.
Naysayer, for a person who denies or opposes some matter or who is often negative in his views, comes from the ancient nay, one of two words of negation, the other being no. Which you used depended on the way in which the question was put to you.
If it was framed affirmatively but you wanted to deny its truth, you used nay, much as we might now respond with “definitely not” or “on the contrary”. If it was framed in the negative and you agreed, you used no. This fits with its origin from ne aye, not yes. The reverse used yea and yes. Confusingly for us today, the parallel form yea was the simple term of agreement, while yes was the positive equivalent of nay, meaning “it is so”.
So somebody who asked you “Is he an honest man?” needed the reply “nay” if you thought that, on the contrary, he was a crook but “yea” if you agreed that he was indeed trustworthy. If the query was framed in reverse, “Is he a dishonest man?”, the answers would be either “no” or “yes”.
We have long ago lost this extended system, though it is known in other languages, such as the French si, which like oui means “yes”, but contradicts a question posed in negative form, and also in the similar German doch. Nay survives in Scotland and northern England as an alternative to no. Yea is now known mainly from the Bible (“Let your yea be yea; and your nay, nay”) though it survives as an archaism in the call for a vote in the US congress, called the Yeas and Nays. But the verb naysay (similar in sense to gainsay) and noun naysayer remain in rude health.
We must hope that they continue to be spelled like that and avoid those equine implications.