The epistemic verbal categories “evidentiality” and “egophoricity” play an important role in the verbal systems of many Tibeto-Burman languages of the Himalayas. In the course of the past decades, our synchronic understanding
of those grammatical categories has been considerably enhanced by numerous descriptive studies. However, little is still known about the diachronic processes that give rise to evidentiality and egophoricity. The article addresses this gap by discussing evidence from Bunan, a Tibeto-Burman language, for which the development of evidentiality and egophoricity in its past tense system can be reconstructed in detail. It is argued that the evolution of the two categories can be explained by reference to two processes: (i) the reanalysis of a resultative construction as an inferential past tense and (ii) the reanalysis of third person agreement markers as allophoric markers. In addition, it is maintained that the concept of Scalar Quantity Implicature is crucial to account for the evolution of the two categories.