The word 厉害 is formed through the conceptual fusion of two characters: 厉, which originally conveyed a sense of severity, rigor, or intensity (like a fierce wind or strict standard), and 害, which meant harm, damage, or a formidable threat. Historically combined, they described something so severely potent or imposing that it could be overpowering or dangerous, akin to a formidable adversary or a harsh natural force. Over time, this core idea of formidable intensity underwent a semantic shift through common usage, where the context of praise (e.g., for a skill so strong it "overpowers" ordinary ability) gradually led to its modern, dominant meaning of "amazing" or "terrific", while retaining its original sense of "fierce" or "severe" in other contexts. Thus, its formation is essentially the evolution of a compound describing overwhelming potency into a term for outstanding excellence.