An example of to gainsay is to go against a popular opinion.
Origin of gainsay
- Middle English gainsayen gain- against (from Old English gegn-) sayen to say (from Old English secgan say)
From American Heritage Dictionary of the English Language, 5th Edition
- From Middle English gainsayen, ȝeinseggen (“to say against, say in opposition to”), equivalent to gain- + say.