Dr Umar Johnson is an American psychologist and public speaker whose passionate, expressive speaking style has made short clips of his talks widely shared online. Lord have mercy is a familiar expression of surprise and disbelief, and in this brief excerpt his theatrical delivery turned it into a reusable reaction sound. It spread through short-form video and meme pages, where creators reuse it to punctuate shocking reveals, awkward moments, and over-the-top reactions. Its brevity and clear emotion keep it useful long after the original clip circulated.