In the rather dryly titled Private Creation and Enforcement of Law: A Historical Case, David Friedman, son of Milton, shares one of my favorite obscure bits of legal history:
In modern law the distinction between civil and criminal law depends on whether prosecution is private or public; in this sense all Icelandic law was civil. But another distinction is that civil remedies usually involve a transfer (of money, goods, or services) from the defendant to the plaintiff, whereas criminal remedies often involve some sort of ‘punishment.’ In this sense the distinction existed in Icelandic law, but its basis was different.
Killing was made up for by a fine. For murder a man could be outlawed, even if he was willing to pay a fine instead. In our system, the difference between murder and killing (manslaughter) depends on intent; for the Icelanders it depended on something more easily judged. After killing a man, one was obliged to announce the fact immediately; as one law code puts it: “The slayer shall not ride past any three houses, on the day he committed the deed, without avowing the deed, unless the kinsmen of the slain man, or enemies of the slayer lived there, who would put his life in danger.” A man who tried to hide the body, or otherwise conceal his responsibility, was guilty of murder.
There’s much more to the article, and I recommend reading the whole thing.