A short handheld weight held one in each hand for strength training is called a dumbbell.
Dumbbells are free weights built around a handle with weight at both ends. They are commonly used singly or in pairs for movements such as curls, presses, rows, lunges, and squats. Because each hand controls its own weight, dumbbell exercises can expose strength differences between the left and right sides and allow a broad range of movement.
The idea has very old predecessors. Ancient Greek athletes used halteres—stone or metal weights—for training and for the long jump. In India, club-shaped weights were used for physical conditioning for more than a millennium. The English word “dumbbell” appeared by the early 18th century; “dumb” referred to a bell-like exercise device that made no sound.
A dumbbell differs from a barbell, which uses one long bar held with both hands. A kettlebell has a single handle above a rounded weight, while a medicine ball is a weighted ball rather than a handled free weight.