The word 堡垒 is formed by combining two characters, each contributing a related meaning to create a single, more potent concept. The first character, 堡 (bǎo), on its own means "fortress" or "stronghold". The second, 垒 (lěi), originally depicts piling up earth or stones to build a defensive wall or rampart. When paired, they do not simply add together; instead, they merge into a unified idea where 堡 provides the core notion of a fortified structure and 垒 intensifies it with the specific imagery and function of its reinforced, piled defenses. The result is a compound word that powerfully conveys the essence of a "fortress" or "bastion", a place built with layered, formidable strength.