paronomasia
noun
par·o·no·ma·sia ˌper-ə-nō-ˈmā-zh(ē-)ə 
ˌpa-rə-;
ˌpa-ˌrä-nə-ˈmā-
: a play on words : pun
paronomastic
ˌper-ə-nō-ˈma-stik
adjective ˌpa-rə-;
ˌpa-ˌrä-nə-ˈma-
Word History
Etymology
Latin, from Greek, from paronomazein to call with a slight change of name, from para- + onoma name — more at name
First Known Use
1577, in the meaning defined above