In Korean, there are many words which have the identical or similar meaning but different honorific usages. The words 'gamsahada' and 'gomapda' (thank) are used differently though they have the similar meaning. Korean speakers think that 'gamsahada', a loanword from Chinese, sounds far more polite than the pure Korean counterpart 'gomapda'. In this regard, for the most time, we use 'gamsahada' for a person with a higher rank than us, instead of using 'gomapda'. By contrast, we can say 'gomapda' to a person who has a lower rank than us. The two words have no difference in the propositional meaning. Nonetheless, the facts that they are used differently in connection with the relation of speaker and hearer imply that they have different functions in the use of honorifics. In this paper, we aim to analyze 'gamsahada' and 'gomapda' from the sociolinguistic perspective. We will use the data of modern Korean corpus of KAIST to understand how the two words are used differently in connection with the relationship between the speakers and the hearers. Furthermore, we identify the difference of usages by means of analyzing that they have what distribution or relative importance at the speech levels of hearer honorifics. This study is not only useful attempt for clarifying the detailed features of Korean honorifics, but also an essential task for understanding the Korean language profoundly.