The word 长久 is formed by combining two characters, 长 (cháng) and 久 (jiǔ), which both independently convey the core idea of extended duration. 长 originally depicted a person with long hair, emphasizing physical length, which was extended metaphorically to mean "long in time". 久 is an ancient pictogram suggesting an object blocking or enduring, inherently meaning "a long time". Their combination is not merely additive but reinforcing and synthesizing, merging the concepts of spatial length and temporal endurance to create a single, more abstract, and emphatic concept of permanence, stability, and long-lastingness.