Yol?u, Aboriginal people from Arnhem Land, Australia are at risk of Machado-Joseph disease, with progressive loss of speech. Yol?u are interested in developing augmentative and alternative communication (AAC) systems in their own languages. This research aimed to develop a culturally responsive process to explore and create a core vocabulary word list for Yol?u adults living with the disease for inclusion in AAC system prototypes. A list of 243 Yol?u words and morphemes was created. In this highly collaborative, mixed methods, participatory action research, "Balanda" (the Yol?u word for non-Aboriginal people) and Yol?u researchers conducted cycles of transcription and analysis of a language sample, with oral group discussions to identify which words to include, omit, or add, based on Yol?u perceptions of the structure and use of their languages. A Yol?u metaphor, "Gulaka-buma" ("Harvesting yams"), was identified by Yol?u researchers to represent and share the research process and findings. Three key themes were identified that summarize the main cultural and linguistic considerations related to changes made to the core vocabulary. Study findings emphasized the role of language as an expression of culture and identity for Indigenous peoples and the importance of considering cultural and linguistic factors in selecting vocabulary for AAC systems.