This paper uses a bibliometric method to analyse the vocabulary research published in the journal "System" between 1976 and 2017. The bibliometric method used here is co-citation analysis, an approach which allows us to map the influences that have significantly impacted on vocabulary research. The analysis is intended to expand on an earlier analysis by Lei and Liu (2019), which studied the outputs in "System" but also analyses the features of all the papers published in the journal. This paper identifies five main clusters in the "System" data set. It also reports how these clusters grow and change over time. It argues that the data point to the emergence of a first paradigm in vocabulary research (Kuhn, 1971), and suggests some ways in which this paradigm might shift in response to demographic changes among the researchers who publish in "System."