The traditional diachronic treatment of the Korean honorific marker LsupL is that LsupL was originally used as a referent honorific marker from the subject’s point of view. It then underwent changes to become a speaker-addressee-oriented (S-A) marker. Diverging from this traditional approach, this paper claims, based on a large-scale corpus-based study, that LsupL was used as a speaker-oriented marker as early as the fifteenth century. To account for Lsup-’s function change, it posits three stages for the evolution of the modern usage of LsupL. In Stage I (fifteenth century), LsupL was used to establish an honorific relation between a speaker and a referent. In a later transition stage (Stage II, sixteenth century), LsupL began to be used with the contextual restriction that the referent be the same as the addressee. Due to its high frequency, this use of speaker-addressee honorification was coded as a new standard (Stage III). This paper shows that the pragmatic function change of the Korean honorific marker is adequately accounted for by Traugott’s (2003, 2007) (inter)subjectification theory.