Over the last 25 years, there has been significant modernisation and elaboration of the Maori language mathematics lexicon and register to support the teaching of (Western) mathematics as a component of Maori-medium schooling. These developments are situated within the wider Maori language revitalisation movement in Aotearoa/New Zealand, of which Maori-medium education is a central component. A feature of the initial development of a Maori mathematics lexicon was the informal approach taken, involving elders, teachers and community working together to establish a corpus of appropriate terms, rather than any formal language planning approach. Subsequently, two state agencies, Te Taura Whiri i te Reo Maori (the Maori Language Commission) and the New Zealand Ministry of Education assumed a formal role in the standardisation and elaboration process. Due to limitations in resources and expertise, the Commission eventually withdrew from the process of developing the specialised lexicon for schooling and, in their absence, ongoing lexical development was entrusted to a group of Maori-medium mathematics educators (Te Ohu Pangarau) and closely linked to the Ministry of Education's numeracy strategies. However, the process of linguistic modernisation of the Maori language to support the teaching of school subjects such as mathematics has since raised a number of conflicting tensions and linguistic issues, particularly among the older generation of Maori language speakers. This paper explores the process of development and the at-times conflicting linguistic ideologies which influenced the lexication and codification of the Maori-medium mathematics terminology. It also specifically examines the roles, policies and beliefs of the agents, including the two state agencies, involved in the process, charting the connections between micro, meso and macro language policy and practices in this context.