A few years ago in a course on Medicine for Scientists and Engineers we spend a while looking at the parts of Medical vocabulary and seeing often by understanding the Latin roots of a word you could figure out what it meant. Occasionally its not that easy. For example the word "orthopedic" has the roots ortho- and -ped- in it. "Ortho" means straight, and "ped" can mean either foot or child (not sure how that works). So orthopedics should have something to do with straightening feet or straightening children, and originally it must have been coined in that context. Now it refers to "A branch of medicine that focuses on injuries and diseases of the musculoskeletal system (the body's muscles, skeleton, and related tissues), including the spine, joints, ligaments, tendons, and nerves." (link) Essentially, there is some straightening and/or fixing of bones and muscles going on.
So thats a term thats drifted a bit from its original meaning. However, the real drift comes in the way the word 'orthopedic' has been commandeered by companies in search of medical sounding trademarks. I'm thinking specifically of Sealy's 'Posturepedic' mattresses. Sadly, they've taken the wrong part of the word 'orthopedic' for their product. Their mattresses apparently promote posture for kids and/or feet. Maybe they should change the name to Sealy Postorthotic Mattresses.