"liquid food," 1650s, from French soupe "soup, broth," from Late Latin suppa "bread soaked in broth," from a Germanic source (cf. Middle Dutch sop "sop, broth"), from Proto-Germanic base *supp-, from PIE *sub-, from root *seue- "to take liquid" (see sup (v.2)). Primordial soup is from a concept first expressed 1929 by J.B.S. Haldane. Soup kitchen is attested from 1839. In Ireland, souper meant "Protestant clergyman seeking to make proselytes by dispensing soup in charity" (1854).
"increase the horsepower of an engine," 1921, probably from soup (n.) in slang sense of "narcotic injected into horses to make them run faster" (1911), influenced by supercharge (v.).