peer reviewed ; The present contribution offers an attempt at reconstructing the early history of the controversial notion of separable complex verb (SCV). Late Renaissance dictionaries of Dutch, which list great numbers of SCVs, lemmatise and represent them as words, not as syntactic constructions. However, material collected from Thesaurus Theutonicae linguae (Antwerp, 1573) allows to hypothesise that at least some of such ‘verbs’ are artificial constructs, whose proper interpretation depends on the meaning of the term praepositio. The initial design of Dutch-French-Latin Thesaurus, which has often been regarded as the first fully-fledged dictionary of Dutch, was intended to meet the needs of Dutch learners. Accordingly, Dutch grammar occupies a prominent place in it. Yet, the bulk of grammar comments found in Thesaurus deals with praepositiones. The great interest, which Early Modern Flemish lexicographers show in this word category, can only be explained by taking into account the role of praepositiones within verbal morphology/syntaxis. A closer examination of praepositio in Thesaurus reveals that this term encompasses multiple syntactic patterns, thus explaining how a word group such as SCV could be assimilated to a lexeme. Although never reprinted, Thesaurus constituted the principal source of several Renaissance dictionaries, thus imposing its conception of praepositio and complex verb on later generations.