This study investigates a second language (L2) speaker's use and learning of the Icelandic auxiliary verb "aetla" (pronounced /aihtla/) in the wild. This analytic focus is motivated by the L2 speaker's (Anna) own orientation to "aetla" as a learnable. We track Anna's use of "aetla" in naturally occurring social interaction over time. Anna first learns to use "aetla" to make requests in service encounters but this does not automatically transfer to other environments, suggesting an intricate relationship between "aetla" and the social action it is used to accomplish. The study illuminates: (1) how this relationship between "aetla" expressions and the social actions they are used to accomplish develops over time; and (2) how Anna's increasingly diversified and productive varieties of "aetla" expressions co-emerge with increasingly varied action accomplishment. Together, these two dimensions of L2 learning form the backbone of Anna's L2 grammar as an emergent accumulation of semiotic resources for social action. This serves as the backdrop for the article's implications for L2 education: (1) we promote the idea of exemplar-based and interactionally situated L2 teaching; and (2) we call for increased awareness of situated and developing interactional competence and usage-based processes and practices in the education of L2 teachers.