Abstract In this paper we analyse a family of compound constructions in Persian that show two interesting properties: (1) they split into two semantic patterns, human agent noun and instrument noun, and (2) they display categorial ambiguity between noun and adjective. The compounds in question, which are formed with the verbal stem -yāb ‘find’, are collected from diachronic and synchronic corpora and analysed in the framework of Construction Morphology (Booij 2010). We argue that the instrumental pattern is an innovation under the influence of loan-translated English instrument nouns. This pattern dovetailed with a much older morphological construction for human agent nouns. This raises questions about the relation between the two constructions in the contemporary speaker’s lexicon. For the dual functionality of the words as nouns and adjectives, we argue that it can be understood as a second order schema (Booij & Masini 2015) or sister construction (Jackendoff & Audring 2019, 2020), whereby no precedence is ascribed to either of the two patterns.