The concept of ‘becoming" or ‘change-of-state" constitutes a conceptual primitive, and its significance is mirrored in the formation of linguistic systems at the levels of lexis and grammar. Korean exhibits a wide array of lexical semantics, e.g., ‘change’, ‘be good’, ‘succeed’, etc. and of grammatical functions, e.g., Passive, Causative, Resultative, Permissive, etc., that developed from the verb toy- ‘become". These lexical and grammatical meanings form an intricate conceptual network through interplay of pragmatic inferences and (inter) subjectification. Drawing upon historical and contemporary corpus data, this paper explicates the emergence of the polysemous structure of toy-, its grammaticalization paths, and the cognitive mechanisms, from cognitive and discourse-strategic perspectives.