The word 难道 is formed through the conceptual fusion of its two component characters: 难 (nán), meaning "difficult" or "hard", and 道 (dào), meaning "to say" or "to speak". Historically, it literally expressed the idea of something being "hard to say" or "hard to articulate", which over time evolved through usage into a fixed compound. This evolution abstracted the original literal meaning into a rhetorical function, where it no longer comments on the difficulty of speech but instead frames a following statement as a challenging or surprising question, implying "could it possibly be that...?" Thus, its formation is a process of semantic bleaching and specialization, where a concrete phrase solidified into a single unit with a new, more abstracted meaning.