The word 彻底 is formed through the conceptual blending of its two component characters. 彻 (chè) originally conveys the idea of penetrating through or being thorough, often in a spatial sense like water flowing through. 底 (dǐ) means the bottom, base, or foundation of something. When combined, they create a powerful metaphor: to reach all the way to the very bottom and penetrate it completely. This fused image of exhaustive depth gives rise to the abstract meaning of "thoroughly", "completely", or "utterly", as if an action or state leaves no part untouched or unexamined, from the top all the way down to the absolute foundation.