Nay means “denial or refusal” or “a negative reply or vote” according to Merriam-Webster dictionary.
Yea means yes. Yay is an interjection used as a celebratory word.
Yea and yay are two words that are pronouned the same but which have different meanings. They both rhyme with such words as say, or way, or hay, which make them homophones.
It is believed to have first appeared in writing in 731. In biblical translations, it is often used to convey the affirmative as in the word indeed.
According to the Oxford English Dictionary, the first known usage of the word yay goes back only to 1963, but 19th-century examples have been uncovered.