The form fu(variant u) fulfills several functions. It is a preposition selecting NPs and clauses, tensed or infinitival. It is a mood marker occurring either between the subject and the verb, or before the subject. It is a complementiser selected by predicates of thewant-class; as such it is in a paradigmatic relationship with other complementisers in the language. Finally, in some contexts, fu appears to function as a case marker, rather than as a preposition, as it may be associated with several thematic roles. The first objective of the paper is to provide a detailed inventory of all the functions off u and a detailed description of its properties for each of its functions. This will be done mainly on the basis of published sources. The proposal that fu can head various syntactic projections (P, Force, Fin, Mood, Kase) will be shown to account for its multifunctional character. The second objective of the paper is to discuss the origin of the properties of fu. First, the grammaticalisation scenario proposed in the literature is considered. In this scenario, the preposition fu would have been reanalysed as a complementiser. It is argued that this scenario is not an optimal one. Second, we consider a relexification scenario along the lines of Lefebvre (1998b). Although the form of the lexical item in question is derived from English for, as has been noted by several authors, most of its other properties cannot be derived from this lexical item. A comparison of the properties of fu with those of corresponding lexical items in one of the substratum languages of Saramaccan, Fongbe (e.g. Smith 1987), yields a different conclusion: while the form of the Saramaccan lexical entry is derived from English, the bulk of its semantic and syntactic properties are derived from those of corresponding substratum language lexical entries. The properties of the creole lexical entry thus appear to follow from the relexification account of creole genesis. In this case, however, two substratum lexical entries (nú, preposition and complementiser, andní, mood marker and complementiser) appear to have been relexified on the basis of a single superstratum formfor, yielding the creole lexical entry fu cumulating all the functions of the two substratum entries. Some details distinguish the creole lexical entry from the two substratum ones. It will be shown that the make up of fu has also involved some reorganisation of the original lexicon, and some innovation.