Since mitts were introduced to baseball in the 19th century, every player on a team uses one. Before that, players used their bare hands or improvised gloves with the fingers cut off to slightly pad the catching hand. Today's mitts are wide and sturdy. An oven mitt isn’t helpful in baseball, but it also protects hands. In fact, mitt can also mean "hand" informally: "Get your mitts off my chocolate cupcake!"

Source: Vocabulary.com