The word 本人 is formed by the direct conceptual combination of its two component characters: 本, which carries the core idea of "root", "origin", or "fundamental", and 人, meaning "person" or "human". Together, they create a compound where 本 acts as a modifier to 人, specifying not just any person, but the essential, original, or primary one, hence arriving at the meaning of "oneself", "the person in question", or "I myself". It is a semantic fusion where the first character defines the specific nature of the second.