The word cloak was borrowed into English around the turn of the thirteenth century with the spelling cloke. Throughout Middle English, it also took the forms of clooke, clocke, cloik, clok, cloak, and cloake until cloak was standardized in the 1700s. It comes from the Old North French word cloque, which still meant "cloak", and that's from Medieval Latin clocca, or "bell". The connection was that cloaks back then were thought to have bell-like shapes (this also makes it a relative of the word clock). Beyond that, the etymology is unknown, but it's thought that it could ultimately be a Celtic word spread by Irish missionaries, and it would ultimately be onomatopoeic in origin. The phrase cloak and dagger is an 1848 calque of a French phrase and the verb to cloak emerged from the noun in the early sixteenth century.
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.