The dumbbell originated as an object used for exercising the muscles that had the shape of the tool used to ring a church bell. So it is not a bell at all. Since there is no bell, the reference to being dumb, silent. That word came into use in the early 1700s. The dumbbell evolved from halteres, used in ancient Greece as an exercise weight. A club shaped weight, called a nal, was used in India for over a millennium
Athletes in ancient Greece used halteres (original dumbbells) to enhance their long jump. They would swing the weights as they ran toward the long jump start, leap as they swung the weights forward and swing back, letting go as they were at the peak of their jump. Done well the extra momentum gained from those swinging weights lengthened their jump. A great bit of trivia here for you
The dumb in dumbbell refers to absence of sound. A dumb bell cannot ring. The transfer to labelling a person as a dumbbell infers that this person does not know about something or other and thus is silent, dumb. That grew into a generalization about not being smart at all, knowing virtually nothing. Calling someone a dumbbell is an extremely harsh accusation. Yet, some do label others as such
Pool dumbbells are used for strength training where muscles are used to work against buoyancy. So a pool noodle or any floating item can be a dumbbell. One popular variation is a pull buoy, a float attached to the leg, used to strengthen swimming. Hmmmm, I just never thought of a floatie as an exercise tool. Did you? Maybe these dumbbells aren’t so dumb after all. Fun
A variation of the dumbbell is the barbell, a long bar with weights at each end. A barbell is meant to be used with both hands lifting and releasing it. A dumbbell is meant to be used with one hand, though it is often used in pairs, one in each hand. Using a barbell is more likely to produce muscle growth that is balanced, same on both sides of the body. That kind of symmetry is prized by body builders.