The word "说不定" is formed through a conceptual fusion where the action of speaking or stating ("说") is combined with a negation ("不") of certainty or fixity ("定"), creating a compact unit that metaphorically represents the idea that something cannot be definitively stated or pinned down. It evolves from a literal verbal phrase meaning "cannot say for sure" into a single, solidified expression that encapsulates the inherent uncertainty of a situation, effectively packaging the abstract notion of unpredictability into a familiar, action-oriented framework.