The word "瓮城" is formed by combining the character "瓮", meaning a jar or urn, with "城", meaning city wall or fortress. This compound term literally translates to "jar city wall", referring to a fortified enclosure built outside a city gate. The name derives from the enclosure's shape, which resembles a jar, with the first character "瓮" describing this form and the second character "城" denoting its defensive function as part of the city's structure.