Dictionary.net

wun'y[.e]r, n. (1 Hen. IV., II. i. 84) probably a person that converses with great ones--hardly, as Malone explains, an accountant of the exchequer, a banker. [No doubt formed from one, like lawyer, sawyer, &c. Malone over-ingeniously refers to the mark o.ni., an abbreviation of the Latin form oneretur, nisi habeat sufficientem exonerationem ('let him be charged unless he have a sufficient discharge'), or explains as a misprint for moneyer.]