Despite its appearance, the exclamation P.U. (used in reaction to unpleasant odors) is not actually an acronym. It comes from a seventeenth-century word that could be spelled pue, peugh, pew, pue, and pyoo, and was pronounced pew. Over time, the pronunciation morphed into pee-yew because of people humorously extending the sound. Then, because it sounded like the letters, people mistakenly changed the spelling to look the way it does today. There are several theories as to the etymology of pue/peugh/pew/pue/pyoo: it might derive from the Spanish interjection fu, which is used to show disgust; it might come from the French verb puer, meaning "to stink"; it might be a variant of the exclamation phew, and/or it might somehow trace to Latin verb putere, also "stink".
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.