 The interaction is called 'charged' because the W bosons coupling to the charged currents must have electric charge.The charged current that gives the interaction its name is that of the interacting particles, in a charged combination.For example, the charged-current contribution to the → elastic scattering amplitude
where the charged currents describing the flow of one fermion into the other are given by

Charged current interaction is the most easily detected of the interactions of the weak force.