The word 大火 is formed through the direct and literal combination of its two component characters: 大 (dà), meaning "big" or "great", and 火 (huǒ), meaning "fire". These individual pictographic and ideographic elements are fused in a straightforward, conceptual compound where the first character modifies and intensifies the second. The resulting meaning is not merely "big fire" as a phrase, but a single, consolidated concept that inherently carries the sense of a major conflagration, a significant blaze, or, by extension, great fame or popularity (metaphorically "spreading like wildfire"). Its formation is purely semantic, building a new, unified idea from the sum of its visual-meaning parts.