firefly, glow-worm, glimmer

螢 is composed of a variant of 榮 (honor) and 虫 (insect). 榮 is a pictograph of two torches, meaning brightness, while 虫 is a pictograph of a snake, here representing insects. Thus, 螢 refers to an insect that emits faint light, such as a firefly, and is also used to describe other objects that emit a faint glow.