Indefinites display a great functional variety and they give rise to different pragmatic effects. We focus on free choice indefinites and in particular on the Italian qualsiasi. Our aim is to reconstruct the grammaticalization path of this item and understand how diachronic data might shed some light on existing semantic theories of free choice. We employ corpus-based tools to build a database containing occurrences of qualsiasi from its origin and early forms to its current usage. We show that qualsiasi emerged from a particular unconditional construction and we outline the different stages which led to its grammaticalization. We analyze the compatibility of our diachronic study with formal accounts of free choice inferences, with a focus on Alternative Semantics analyses for indefinite pronouns and so-called grammatical theories of free choice. Our work shows that an integration between formal semantics and historical linguistics is fruitful and worth pursuing.