Knives are weapons as well as tools, but in the prehistoric origins of the knife there was probably very little separation between those two uses. Our ancestors had a need to cut and puncture things in order to survive, and sometimes those things happened to be someone else’s ancestors.
It probably wasn’t until the development of sedentary agricultural societies that specialized knives were developed as ‘weapons’ for use against other humans. Hunter-gatherers seldom existed in sufficient numbers or densities to justify their inventing or lugging around specialized tools primarily for use on other humans.
As humans grew more settled and more numerous the knife evolved, first from stone and then from metals, to make all that cutting and puncturing easier. As it did, the uses and designs of knives diverged until they were no longer recognizably descendants of the original flint hand-axe. One-handed grain sickles and bronze spears are both cutting tools, but using the wrong one for farming or fighting will get you killed or starved.
Much of the marketing and allure of knives today comes from their status as ‘weapons,’ but thankfully few of us are called upon to use them in that capacity. Do you consider your knife a multipurpose tool, or is the knife you carry primarily a weapon of self-defense? How is your choice of knives influenced by their intended use?