Denier has the etymological history Formed from the verb deny plus the agentive suffix -er; deny is from Old French denier, from Latin denegare ('to deny, refuse'), from de- (intensive) plus negare ('to deny'). The ancestry passes through Latin denegare and Latin negare. The prefix de- often marks removal, reversal, or downward motion in Latin formations, helping to explain the word's surface structure; the suffix -er marks an agent, instrument, or associated person, so the English form is shaped by recognizable word formation as well as by its inherited or borrowed base. In present use as a noun, it means "a person who refuses to admit the truth of something", keeping the historical formation close to the word's ordinary semantic work. Related words include deny and denial.