It strikes me as odd that hypothermia is such an important concept whenever dealing with the world outside our protective shell of modern technology, yet our word for it is long and Latinate. It wasn't even coined until 1886! Why isn't there some gritty little Anglo-Saxon word for it?
"freezing to death"
That there is no single word I can find in a quick check of Bosworth and Toller for hypothermia in anglo saxon does suggest a couple of things: 1) that the literary sources we have in anglo saxon, mostly government documents and a few surviving stories, simply didn't mention it, and that back that far, they didn't really have much of a post-mortem vocabulary.
One of the most common causes of hypothermia is falling into cold water -- such hypothermic deaths would probably be classified as drowning. Non-water related hypothermia -- unusual in the case of a healthy adult -- would most likely be attributed towards old age, "being sickly," "being poor," or some other non-scientific description, including "he just died," and "froze to death."
The etymology of "hypothermia" shows its origin in the 19th century, which means even modern english didn't have a single word for it until relatively recently -- certainly much after the suppression of anglo-saxon, and not until well into the modern era of science.
--doug