c. 1300, bordel "house of prostitution," from Old French bordel "small hut, cabin; brothel" (12c.), diminutive of borde "hut made of planks," from Frankish *bord "wooden board" or some other Germanic source related to board (n.1). The modern form (1590s) is a result of the French word being borrowed by Italian then passed back to French with a suffix and re-borrowed into English.
<a href="https://www.etymonline.com/word/bordel">Etymology of bordel by etymonline</a>
Harper, D. (n.d.). Etymology of bordel. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/bordel