The definition of a camp knife is a big, heavy knife that can do most of what a hatchet can do and much of what a knife can do. The concept is not new. Mountain men carried heavy butcher knives (and skinners, and patch knives), which would qualify nicely as camp knives. In 1849, the Ames Manufacturing Company in Massachusetts manufactured a Rifleman’s Knife for American soldiers, and today we’d call it a camp knife. In World War II, the Marine Corps issued a Hospital Corpman’s Knife to medical personnel, and a Bowie knife made by Western Cutlery, the W49, to some of its Raider units. (This is the knife that Robert Redford carries in Jeremiah Johnson.) Both would qualify as camp knives, and both are very useful.
In all likelihood, “camp knife” became an official term when the late, great Bill Moran forged his own versions, and the writer Ken Warner picked up on the term and gave it to the rest of us.