late 15c., "fountain, stream," probably from Middle French sourge-, stem of sourdre "to rise, swell," from Latin surgere "to rise," contraction of surrigere "to rise," from sub "up from below" + regere "to keep straight, guide" (see regal). Meaning "high, rolling swell of water" is from 1520s; figurative sense of "excited rising up" (as of feelings) is from 1510s.