The loin is the part of the body on either side of the spine, between the ribs and hips. When a doctor asks if your back hurts, they might press gently on your loins to check for soreness in that lower back area. In animals, this is the part that provides some of the most tender cuts of meat, which is why you'll see pork loin or beef loin at the butcher's counter.

In older writing, you might encounter the phrase “gird your loins,” which meant to prepare yourself for hard work or a difficult challenge. Ancient people wore long, flowing robes, and before running, fighting, or doing heavy labor, they would gather up the fabric and tuck it into their belt so it wouldn't get in the way. Girding your loins meant literally tying up your clothes around your midsection, but the phrase came to mean getting yourself mentally and physically ready for something demanding. Today, someone might say it jokingly before a big test or challenging game: “Time to gird my loins for that math final!”