Substituting uncover for cover is not even required to make a sexual joke: see acception 6a in https://www.merriam-webster.com/dictionary/cover https://www.merr

Substituting uncover for cover is not even required to make a sexual joke: see acception 6a in https://www.merriam-webster.com/dictionary/cover https://www.merriam-webster.com/dictionary/cover