Because he is an ass, and may be akin to the Cokeses?
1614 November 10 (first performance; Gregorian calendar), Beniamin Iohnson [i.e., Ben Jonson], Bartholmew Fayre: A Comedie, […], London: […] I[ohn] B[eale] for Robert Allot, […], published 1631, (please specify the page)