The word 不愧 (bùkuì) is a grammatically fixed compound formed through a standard negation-plus-verb construction, where the negative adverb 不 (bù, "not") modifies the verb 愧 (kuì, "to feel ashamed"). Literally meaning "not ashamed," its meaning has evolved through lexicalization into a cohesive, idiomatic expression used as an adverb meaning "to be worthy of" or "to deserve the title/reputation." It is almost exclusively used in the set pattern "不愧为..." or "真不愧是..." to praise someone or something for living up to a high expectation or name, thus demonstrating how its constituent morphemes fused into a single semantic unit with a specialized, positive evaluative function.