pun

pun, a humorous use of a word in such a way as to suggest different meanings or applications, or a play on words, as in the use of the word rings in the following nursery rhyme:

Ride a cock-horse to Banbury Cross,
To see a fine lady upon a white horse;
Rings on her fingers and bells on her toes,
She shall have music wherever she goes.

Common as jokes and in riddles, puns also may be used seriously, as in John Donne’s “A Hymne to God the Father”:

Sweare by thy selfe, that at my death thy sonne
Shall shine as he shines now, and heretofore;
And, having done that, Thou haste done;
I fear no more.

This quatrain contains two puns, son/sun and done/Donne.