Besides its main use as a form of the movement verb ir ‘to go’, the Spanish form vaya (lit. go) is also used as a verbal discourse marker. Here we trace this transition from a purely verbal form to a discourse marker by searching a historical corpus of documents in Spanish, which reveals the increasing use over time of vaya in exclamatives to replace a presentational construction. We focus on vaya in isolation and in combination with an indefinite DP or a bare NP. We analyze the meaning of vaya as an epistemic discourse marker, by means of which the speaker expresses a judgment, a subjective epistemic and evidential evaluation of a proposition accessible from context. We postulate that these constructions sit in a Judgment Phrase at the syntactic-pragmatic interface (Krifka 2020), a position to which vaya also moves when its meaning is that of an expressive intensifier that directly modifies over one or more (contextually salient) properties of the noun contained in the DP/NP.