The earliest recorded mention we have of the word crush in a romantic sense is from an 1884 diary of Cairo, Illinois resident Isabella Rittenhouse, who wrote that "Wintie is weeping because her crush is gone". It's thought that this sense of the term developed from the prior slang word mash (this had been recorded earlier with the same definition), since crushing and mashing were similar verbs. Outside of that, it seems like the word crush entered the English language at some point during the fourteenth century. Early spellings included cruschen, cruschyn, crusshe, and crousshe, and it comes from the Old French verb croissir, with the same meaning. Beyond that, it could be from the Frankish word krostjan ("to gnash") or from an unattested Latin word meaning "brush", but that's all uncertain.
Hello! I'm Adam Aleksic. This year, I graduated from Harvard University with a degree in Government and Linguistics. There, I co-founded the Harvard Undergraduate Linguistics Society and wrote a thesis on Serbo-Croatian language policy, magna cum laude. In addition to etymology, I also really enjoy philosophy, trivia, vexillology, geography, board games, conlanging, art history, and law.