This study was to explore the semantic relations among the verbs, meaning act of excretion, such as ‘boda’, ‘nuda’, and ‘ssa-da’ from a historical perspective. The ‘nuda’ was used for the entire data of Korean language history as a verb that most indiscriminately reveals the act of excretion. In case of ‘boda’, this study was to capture the lexicons to express the excretions by euphemism from the data of Middle Korean and the aspects of using them together. Based on these results, this study was to assume that the ‘boda’ was a verb that reveals the act of excretion by euphemism. And, in case of ‘ssa-da’, the meanings of Middle Korean and modern Korean were different. This was because in medieval Korean, it meant that it was abnormal excretion of humans, while in modern Korean, it meant that a child was not toilet-trained. In addition, the meaning of ‘ssa-da’ even referred to the case of normal bowel movements in modern Korean, which was explained as semantic extension of ‘ssa-da’. This study, of course, was to suggest together the fact that the previous meaning of ‘ssa-da’ still remains in data of our modern Korean.