The morpheme po55 in the Yanzhou (Jiande) dialect functions as either a verb of giving or an object marker (Cao 2017). In the former case, po55 patterns with the ditransitive verb gěi in Mandarin Chinese, where the mode of transfer is semantically underspecified, while in the latter case, po55 marks distinct thematic roles of the post-po55 NP, akin to bǎ. The multifunction of po55 results from the grammaticalization pathway from verb of giving/helping to object marker, as defined by Chappell (2007). Through the extensive comparison with bǎ and bǎ-sentences in this paper, we argue that the post-po55 NP must be affected in a specific way and is always associated with the resultative state, due to the realization of the event denoted by the VP. By employing the linking framework in Randall 2010, we propose a unified treatment of po55 based on causativity, which ultimately leads to the conclusion that causativity constitutes the crucial component of the underlying Conceptual Structure of po55, while the morpheme po55 is lexicalized as a strict causative item, albeit its dual status in the grammar.