Definify.com

☞ Yes is used, like yea, to enforce, by repetition or addition, something which precedes; as, you have done all this – yes, you have done more. “Yes, you despise the man books confined.”

☞ “The fine distinction between ‘yea’ and ‘yes,' ‘nay' and ‘no,' that once existed in English, has quite disappeared. ‘Yea' and ‘nay' in Wyclif's time, and a good deal later, were the answers to questions framed in the affirmative. ‘Will he come?' To this it would have been replied, ‘Yea' or ‘Nay', as the case might be. But, ‘Will he not come?' To this the answer would have been ‘Yes' or ‘No.' Sir Thomas More finds fault with Tyndale, that in his translation of the Bible he had not observed this distinction, which was evidently therefore going out even then, that is, in the reign of Henry VIII.; and shortly after it was quite forgotten.”