The word "所以" is formed by combining two classical Chinese characters whose core conceptual meanings fuse to create a new idea. "所" originally carried a sense of "place" or "that which", often used to nominalize a verb, while "以" fundamentally meant "to use" or "by means of". When fused, the literal notion is "that by which [something is done]", evolving into a fixed compound that abstractly marks the logical point of origin or reason, thus coming to mean "therefore" or "so", representing the inferred outcome in a relationship of cause and effect.