Delayer is from delay (from Old French delaier 'to put off', from de- + laier 'to leave', perhaps from Latin laxare 'to slacken') plus the agentive suffix -er. The ancestry passes through Old French delaier and Latin laxare. 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 or thing that causes delay", keeping the historical formation close to the word's ordinary semantic work. Related words include delay, delayed, and delaying.