This study entailed an investigation into the unproductive morphological forms in the Indonesian language. This study analyzed these forms’ nature, patterns, and potential linguistic implications to uncover the reasons behind their existence and persistence. The study employed descriptive approached and data-based methodologies, utilizing the SEAlang Library Indonesian Corpus (SLIC) as the primary data source. The results revealed unique features of unproductive morphological forms in Indonesian, characterized by specific affixational patterns, including the morphologically marked infixes {-em-}, {-er-}, {-el-}, and {-in-}. These forms also exhibited semantic limitations limited to particular word classes or semantic domains. Additionally, a confluence of cognitive and linguistic influences contributed to the phenomenon of unproductive word forms. The study also identified boundaries and constraints within morphological productivity, exploring unproductive morphological forms to provide insights into the micro-change of the language. This study’s findings could advance broader aspects of morphological theory and language description.