Quote Originally Posted by gRomoZeka View Post
Actually "хмарь" and "сырь" are words in their own right. Yesenin did not invent them. It's just dialect/colloquial, and such a word choice accentuates his "village" theme in poetry.
Not sure about those words exactly but he did invent many words of third declension, which have never been used before by anybody and anywhere.