Diachronic aspects of Bjokapakha epistemic verbal morphology
The role of nominalisers and copulas
Bjokapakha belongs to the Tshangla cluster of the Trans-Himalayan (Tibeto-Burman) language family and is spoken in Central Bhutan. Like many languages of the Himalayan region, Bjokapakha exhibits a rich system of epistemic functions, centering around the notion of personal or subjective knowledge (a.k.a. egophoricity, conjunct-disjunct or mirativity). Morphosyntactically, the epistemic categories of Bjokapakha are expressed by constructions involving combinations of nominalisers and copulas which exhibit varying degrees of grammaticalisation. This paper presents the epistemic categories of Bjokapakha and examines the genesis of the Bjokapakha epistemic verbal system from a comparative perspective drawing on insights from other varieties of the Tshangla cluster. Furthermore, a first reconstruction of the nominalisers and copulas of Proto-Tshangla is proposed. It will become evident that nominalisers and copulas have played a crucial role in the emergence of epistemic verbal morphology of Bjokapakha and still constitute productive means for the grammaticalisation of new epistemic categories.