Has O.Henry made an error in his use of "wot", which I find is first and third person singular. It seems to me that he
should have used third person plural. What would that be?

"Thus does one sister of the plain gold band know another who stands in the enchanted light that shines but once and briefly for each one. By rice and satin bows does mere man become aware of weddings. But bride knoweth bride at the glance of an eye. And between them swiftly passes comfort and meaning in a language that man and widows wot not of.