The word 坚固 (jiāngù) is formed through a common Chinese morphological process called synonymous compounding, where two characters with similar meanings are combined to reinforce a single concept. The character 坚 (jiān) primarily means "hard", "strong", or "firm", while 固 (gù) means "solid", "secure", or "immovable". When paired, they create a compound adjective that intensifies and nuances the idea of sturdiness, solidity, and resilience, often used to describe physical objects like structures or materials, as well as abstract concepts like friendships or defenses.