Hard and Soft
Yeah, I know. You'd probably never even heard of osteomalacia before now. I hadn't, either, until I followed a Pharyngula link to a Huffington Post page full of medical quackery regarding H1N1, aka swine flu, and every time I look at "H1N1" I can't help but pronounce it "heinie". Anyway, the HuffPo doctor recommends homeopathic remedies, so you know he's talking out his ass: homeopathy doesn't work and can't work, and I'm not going to get into why; you're on the Internet, you can do the research.
At any rate, the doctor used the word "osteomalacia", which means "softening of the bones", and of course you know that "osteo-" is Latin for "bone", as in "osteoporosis", porous and therefore brittle bones. But what of "-malacia"?
It really did take a lot of digging, but I eventually surmised, and then discovered for a fact, that the meaningful part of "-malacia" was a very productive Indo-European word stem which is actually "mel-", "soft", but which often shows up in altered forms as "-mol-" or "-mal-" or even "-mil-".
Some other mel- words: "mollusk", which is soft and squishy inside its hard shell; "melt", which is to say "become soft"; "emollient", "having a softening effect"; "mild"; "smelt", to melt down metal; and "enamel", a melted-down porcelain paste. But not, unfortunately, "malleable", which, though it means "soft", actually means "able to be beaten into shape by a hammer", since the "mal-" of "malleable" is related to "mallet", from Latin "malleus", "hammer".