The word "恐惧" is formed through the combination of two characters, "恐" and "惧", which both independently carry the core meaning of "fear" or "dread". This is a classical Chinese lexical formation where two semantically similar or nearly synonymous characters are paired together to create a single, reinforced concept. The process intensifies and solidifies the abstract emotion, resulting in a compound word whose meaning is the amplified and unified sense of profound fear or terror conveyed by both components.