Origin of the Proton Mass? Heavy Quarkonium Production at Threshold from Jefferson Lab to an Electron Ion Collider

In this article we discuss the science enabled by heavy quarkonium production in electro-and photo-production on a proton, its possible relation to the determination of the trace anomaly contribution to the proton mass, and the search of LHCb charm pentaquark. We describe the elastic threshold J/ψ production experiments carried out or planned at Jefferson Lab. We also discuss a possible elastic threshold ϒ electroproduction measurement on a proton at a future electron ion collider (EIC).