In Korean with its detailed and specific honorific system one has to be very careful in selecting address and pronominal forms. Otherwise conflicts could arise between interlocutors. To avoid such a situation, Koreans developed various means of address, pronominal forms and their substitutes. The general tendency of human languages that highly-valued expressions are devaluated over time seems to have played an important role in these developments. In the history of the Korean language, we observe that the address and pronominal forms are very often devaluated and eroded or replaced by new forms. In this paper, such changes are accounted for by proposing three pragmatic principles based on the dynamic relationship between the speaker and the hearer. This relation is thus regarded as an important parameter within a process of grammaticalization.