Nuts.

People with nut allergies can die from eating nuts. Being hit in the nuts hurts (I speak from experience. Painful, painful experience). You eat nuts (unless you’re allergic, in which case you should run away). If someone says you’re nuts, it doesn’t mean you’re a peanut or an almond. Nuts and bolts hold things together. A climber’s nut or chock wedges into a rock. Instead of swearing, you can say, “Aww nuts!”. And finally, the nut on a violin is a small piece of hard material that supports the strings.