'披甲' literally means 'to wear armor' — 披 (pī) means 'to drape over' or 'to don', and 甲 (jiǎ) means 'armor' or 'shell'. Together, the term evokes the image of a warrior putting on protective armor before battle. Though historically used for human soldiers, in modern Chinese it’s most commonly applied to animals with natural protective coverings — especially crustaceans like crabs and lobsters, whose hard exoskeletons are poetically described as 'worn armor'.

The phrase carries a literary, slightly formal tone and appears frequently in nature writing, biology textbooks, and descriptive essays about wildlife. It emphasizes resilience, defense, and innate protection rather than mere physical appearance. While it can occasionally refer to humans in historical or poetic contexts (e.g., ancient generals), its dominant contemporary usage is zoological — highlighting evolutionary adaptation through metaphorical armor.