To any Indologist, 'Instructie off Onderwijsinge der Hindoustanse en Persiaanse talen' (1698) is instantly recognizable as the iconic ‘first grammar of Hindustani’ – just as the name of its author, Joan Josua Ketelaar, is familiar to scholars of Dutch colonial history. However, the significance of Ketelaar’s work has never been fully appreciated until now. This multifaceted study is a tribute to a rather special Dutch East India Company merchant, and to the exceptional piece of work he created. For the first time, two recently discovered manuscript copies of the text (Utrecht MS and Paris MS) have been examined and compared with the one previously known (Den Haag MS). One of the most significant findings is the identification of models for both the grammatical part and the thematic vocabulary. The origin and purpose of Ketelaar’s work is reflected even in his choice of metalinguistic terminology. From the seemingly random lexical elements, a more complete picture emerges of the socio-cultural landscape in which Ketelaar wrote his introduction to Hindustani and Persian languages. This study aims to put more history into linguistics, and more linguistics into history. It does so by situating the 'Instructie' in the historical context of other linguistic productions created by employees of the Dutch East India Company in Asia, to demonstrate how Ketelaar can be regarded as a link between the academic Latin-speaking community in Europe and the less literate merchants working overseas who sought practical knowledge of foreign languages to be used in daily trade dealings.