What are some profanity words in classical Chinese? It is easy to find profanity words for modern Chinese, but I could not find any profanity words for classical Chinese. Even such simple ones as "to fuck". Please help to promote this knowledge.
As to classical Chinese in the strict sense I know no examples.  Going up to 8th century, The poem "To send far way" by Li Bai (701--762), also known as Li Po, contains two lines translated by David Hinton as

We made clouds and rain love our farewell,
Then nothing but autumn grasses remained.

I cannot find the Chinese on line.  The expression is often traced back further to a classical work "Gao Tang Fu/高唐賦" (for which my historical source is https://fr.wikipedia.org/wiki/Song_Yu) and you can see the original at https://zh.wikisource.org/zh-hant/高唐賦.  But that work only sets up a vague association between sex, clouds and rain.  The phrase  "clouds and rain/云雨" for sex seems to owe more to Du Fu's Tang Dynasty poem: " Wu Gorge and more clouds and rain the night," see http://baike.baidu.com/view/130025.htm

For whatever reason, the phrase "clouds and rain/云雨" has come to refer to sex.  It is not a verb.

For more, follow the advice of 倪阔乐 above.  I am afraid you will not find what you are looking for.