蛀虫 literally means 'boring insect' — 蛀 (zhù) refers to the action of boring or tunneling into wood, while 虫 (chóng) means 'insect' or 'bug'. Together, they name insects like termites, wood-boring beetles, or moth larvae that damage wooden structures, furniture, or trees by burrowing inside. These pests weaken materials from within, often going unnoticed until significant damage occurs.

Figuratively, 蛀虫 is commonly used in political and social discourse to describe people who secretly undermine an organization, institution, or system — much like how wood-boring insects erode wood invisibly. This metaphor emphasizes hidden corruption, betrayal, or internal decay rather than open opposition. The term carries strong negative connotations and is frequently seen in official media when condemning embezzlement, abuse of power, or moral decline among officials.