loin (n.)
early 14c., "side of the body of an animal used for food," from Old French loigne "hip, haunch, lumbar region," from Vulgar Latin *lumbea, from *lumbea caro "meat of the loin," from fem. of *lumbeus, adjective used as a noun, from Latin lumbus "loin" (see lumbago).

Replaced Old English lendenu "loins," from Proto-Germanic *landwin- (cognates: German Lende "loin," Lenden "loins;" Old High German lenti, Old Saxon lendin, Middle Dutch lendine, Dutch lende, Old Norse lend).

The Latin word perhaps was borrowed from a Germanic source. In reference to the living human body, it is attested from late 14c. In Biblical translations, often used for "that part of the body that should be covered and about which the clothes are bound" (1520s). Related: Loins.