The word 不至于 is formed through a logical, three-step conceptual compounding: it begins with the fundamental negation 不 (not), then combines with 至 (to arrive at or to reach), which conveys the idea of an extreme point or a particular state, and finally concludes with 于, a classical particle that situates the action in a realm of condition or comparison. Together, they sequentially construct the meaning of "not reaching the point of" or "not going so far as to", where the negation blocks the attainment of a typically excessive or undesirable outcome implied by the context.