The phrase "ground swell" refers to a strong public opinion or feeling that starts from the general population and builds up gradually, similar to a wave starting from the ocean floor and rising to the surface. Full definition
I think it's a good way to launch into new markets and develop ground swell. (gapingvoid.com)
Asked what sort of ground swell of support she'd got for making this legal, she skipped to the side and started talking about «stakeholders» — and not, alas, the sort that stand beside doomed vampires — all of whom stood to benefit financially. (slaw.ca)
The accuracy and specificity of Hopper's sky indicate, if nothing else, that it is one the artist had seen, rather than one born of imagination or synthesis [fig. 8][fig. 8] Edward Hopper, study for Ground Swell, 1939, fabricated chalk, charcoal, and graphite pencil on paper, Whitney Museum of American Art, New York, Josephine N. Hopper Bequest 70.339. (nga.gov)