The evolution of the negative coordinating conjunction (‘neither’/‘nor’) from Latin to Modern French instantiates a type of cyclic development that is previously undocumented as such at the level of morphosyntax, viz. a ‘semasiological’ cycle. In effect, the conjunction appears to have taken an almost perfectly circular path. Thus, in Classical Latin, as is consonant with the typological status of that language as a Double Negation language, neque/nec was exclusively used in negative contexts. Medieval French being a Negative Concord language, on the other hand, its negative coordinating conjunction, ne, a direct descendant of neque/nec, was able to develop a full range of weak negative polarity uses. In a range of contexts, ne was thus semantically equivalent to either the additive conjunction et (‘and’) or the disjunction ou (‘or’). By the end of the Classical French period, however, the conjunction (which by then takes the form ny/ni) has lost all of its weak negative polarity uses again, and it is used only in strong negatively polar environments in Modern Standard French. Based on data from the electronic corpora Frantext and Base de Français Médiéval, I analyze the three stages of this evolution. I show that, together with other developments in the French negative system, it falsifies predictions made in the literature and has consequences for the reconstruction of negative systems in less well-documented languages.