Other forms: naysaid; naysays
If you've ever wanted to do something and a parent has told you no, you know what naysay means. To naysay is to to refuse or oppose something: for example, a parent might naysay having a hamburger for dinner.
Naysay is made up of the parts nay and say. Nay comes from a Scandinavian root, and say comes from an Old English root. The word naysay itself, as a verb, was originally from Scottish English, which makes sense when you look at the etymology, as there has been a lot of Scandinavian influence on Scotland and Northern England. Go ahead and blame the Vikings!