In this article I claim that the emergence of the existential proform in early Italo-Romance is motivated by the overt marking of definiteness. The available data from a relatively large corpus of early Italo-Romance texts dating from the thirteenth to the sixteenth century suggest that the overt marking of definiteness, which differentiates Romance from its ancestor Latin, favours the establishment of an existential pattern where the encoding of non-canonical pivots (definite ones) is licensed by a locative anchor. From having the status of locative licenser of definiteness, the proform is thereafter reanalysed as an obligatory marker of the existential construction, and is progressively extended to all types of existential construction.