This study aims to find problems of language change education in textbooks, and examine the improvement of them on the basis of formation of ``-nil subakke eps- (- ㄴ /ㄹ 수밖에 없-)``. Education of language change in textbooks has focused on the results of change rather than its processes or causes. Also, it has presented examples only in an aspect of lexicon. Thus it is necessary to provide description of language change about grammatical units above lexical level, and the causes of language change. To achieve the goal of the study, this paper examined the process that ``- n/l subakke eps- (-ㄴ/ㄹ 수밖에 없-)``, which is pervasively used in modern Korean, is formated in various aspects. First, it looked into its possibility in the aspects of grammaticalization of ``su (수)`` into bound nouns and in the aspects of collocation formation of ``bakke(밖에)`` and ``eps -(없-)``. Lastly, it diachronically viewed at the change of ``n/l bakke su eps-(-ㄴ/ㄹ 밖에 수 없-)`` into ``- n/l subakke eps-(- ㄴ/ㄹ 수밖에 없-)`` by using the theory of Utterance Selection Theory.