This article describes the initial work and next steps for the development of a mathematics curriculum in Ichishkíin, an Indigenous Yakama language. Framed by the Ichishkíin concept of pinak'inut'áwaas (mirror/window), our work seeks to answer the following questions: How are mathematical concepts represented in Yakama culture, and how is Yakama culture reflected in mathematical concepts? How can we respectfully and reflectively craft new Ichishkíin words to express mathematical concepts not reflected in Yakama culture? This is decolonizing work, and joins a growing body of Culturally Sustaining and Culturally Reviving Pedagogies, which center teaching and learning on the lived experiences of students while critiquing culture for the ways it both sustains and diminishes. Given the dominant nature of mathematical culture, a key tenet of our project is privileging Yakama culture and the development of Ichishkíin language. We discuss the values and respect that are foundational to our ongoing collaboration to craft curriculum.