Nominal lexemes undergo in history extensive development in the lexical as well as grammatical domains. Their semantic change involves diverse threads of conceptualization which shows significant aspects of language development. Despite the series of intriguing changes in form and meaning that the Late Middle Korean lexeme kaz ‘edge’ has undergone, encompassing polylexicalization and polygrammaticalization that merit an in-depth analysis, it has not yet received earnest attention to date. Thus, this paper aims to fill the research gap by analyzing the lexeme’s development from Late Middle Korean to Modern Korean from the grammaticalization perspective, drawing upon data from a historical corpus and dictionaries. An extensive diachronic data analysis based on concordance and lexical searches shows that new meanings or functions are so diverse that some of them even form an antonymic relation. Such a wide-ranging semantic and functional diversity is attributable in part to the role of the participating forms in word formation processes such as derivation and compounding but, more importantly, to differential conceptualizations of the source meaning ‘edge’ e.g., entity-internal and entity-external conceptualizations; mapping the ‘edge’ onto different continua, e.g., degree, path, likelihood; and involvement of subjectification, e.g., evaluative-epistemic judgment such as counter-expectation. The innovated meanings resulting from such cognitive operations form a conceptual network. The developmental processes of the lexeme kaz ‘edge’, in general, can be explained with reference to grammaticalization mechanisms, such as desemanticization, extension, decategorialization, and erosion, and some mechanisms are also operative in lexicalization as well. However, erosion, or the reduction of phonetic volume, is not prominent in these changes, suggesting that the principles should be interpreted as tendencies rather than deterministic diagnostics. These findings contribute to a better understanding of the complex relationship between lexicalization and grammaticalization.