What in tarnation is an old American expression blending tarnal and damnation, long used in Southern and Western speech to show disbelief. It was widely popularised by cartoon characters like Yosemite Sam in Looney Tunes, whose blustery delivery turned it into shorthand for comic confusion. Online, the phrase became a reusable reaction clip on meme pages and video edits, detached from any single scene. People now drop it whenever something rural, ridiculous, or inexplicable appears, because the wording itself signals old fashioned shock.