The word diaper was first used in a story about a knight from the year 1350, when it was spelled diapre. After that, it also took the forms dyapre, dyapere, dyaper, dyoper, dieper, dyeper, diapre, and dipar until diaper became the standard during the seventeenth century. The term comes from the Old French word diapre, which specifically referred to a a type of cloth with a repeating pattern (these were often used as diapers). That, through Latin diasprum, traces to the Ancient Greek word diaspros, which was composed of the prefix dia-, meaning "across" or "thoroughly, and the root aspros, "white" (the diapres were typically white). Dia derives from Proto-Indo-European dwo ("two") and aspros was relatively rare but is thought to also be from PIE. The British slang word nappy is a diminutive of napkin.
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.