The Dutch language has never been exclusively ‘Dutch’: throughout its history, Dutch grammar and vocabulary have been enriched by elements from other languages. These foreign influences provide a meaningful feature of historical texts because they signal socio-linguistic norms among language users. Contributing to the historical study of those norms, this paper presents a replicable lexicon-based method for automatic extraction of Latin and French loan words for early modern Dutch. The lexicon consists of 10,457 distinct loan words obtained from three digitised seventeenth-century loan word dictionaries. This paper evaluates and demonstrates automatic loan word extraction through a case study of 33 texts by four seventeenth-century Dutch translators of Early Enlightenment philosophers René Descartes and Baruch Spinoza. Moreover, this method tailored for historical Dutch complements similar tools developed for modern Dutch, thus enabling comparative analysis of foreign influences in trans-historical Dutch corpora.