During the Renaissance poets enjoyed playing with language and making use of the many different meanings of a single word. They would do this to create a complexity of meanings within a single line or two of poetry. Shakespeare employs the use of puns in "Sonnet 135" for a comic effect as the speaker begs the Dark Lady to accept him as a lover. In this poem the speaker puns on the word will, which can mean (1) desires or wishes; but it also quite frequently refers to (2) sexual desire. Of course, the word Will (with a capital W) is a nickname for William. The speaker is also called Will. However, even though Shakespeare uses a version of his own name for the speaker, such usage does not necessarily prove that the speaker is not a fictional character. In any event, by asking the lady to have her will, the speaker is asking her (1) to fulfill her wishes or dreams, (2) to be with him, and (3) to have sex with him. All three meanings are intended.
The use of puns in sonnet cycles does not begin with Shakespeare. The reader may recall that in Astrophil and Stella by Sir Philip Sidney, the poet puns on the word rich (see Sonnet 37). Like the word will, this word was also a name. The real-life model for Stella, a woman named Penelope Devereux, was married to a man named Lord Robert Rich.