Why are beetles called beetles even when their names include firefly or weevil?

Beetles and weevils are both members of the insect order Coleoptera. The term "beetle" is the common name used to describe any insect within this order, which is defined by specific anatomical characteristics, most notably two pairs of wings where the front pair is modified into stiff, protective covers called elytra.312

Because Coleoptera is the largest order of insects, it encompasses a vast diversity of species with varied appearances and habits. Common names like "firefly" or "weevil" are specific identifiers used to distinguish certain families or groups within this massive order based on their unique traits—such as the light-producing capabilities of the Lampyridae (fireflies) or the elongated snouts of the Curculionidae (weevils). Despite these distinct common names, these insects remain biologically classified as beetles because they possess the fundamental physical features that define the order Coleoptera.3421