English speakers expressing futurity have the choice of two primary verb forms, will or be going to (BGT). Previous studies establish that BGT has multiple meanings not associated with will. Langacker (1987) rejected a metaphoric analysis of BGT (time is motion) as inadequate and offered a binary feature analysis. Brisard (2001) expanded on this analysis and argued that manipulating the configurations of binary features explains the semantic differences between will and BGT. However, Brisard’s analysis overlooks the semantic overlap among will, BGT, and the simple present. Moreover, it does not provide a framework that treats will and BGT as part of the larger English modal verb system. Finally, it lacks a persuasive explanation of how the meanings associated with will versus BGT arose. We address these gaps by proposing a polysemy-based explanation that emphasizes invited inferences (e.g., Bybee, Perkins, & Pagliuca, 1994) and embodied experience; a particularly novel aspect of the analysis is that all the meanings of BGT are related straightforwardly to components of the human walk cycle. Further, we argue that the shared future meaning of will and BGT represent inter-lexical polysemy (Evans, 2015b), thus providing additional evidence for the Theory of Lexical Concepts and Cognitive Models (LCCM).