Know how to use "fewer" and "less"? Find out.
c.1300, "rough, shaggy, careworn" (originally of animals), from Old Norse rogg "shaggy tuft" (see rug). "The precise relationship to ragged is not quite clear, but the stem is no doubt ultimately the same" [OED]. Meaning "vigorous, strong, robust" is American English, by 1848.
We were challenged with a peace-time choice between the American system of rugged individualism and a European philosophy of diametrically opposed doctrines -- doctrines of paternalism and state socialism. [Herbert Hoover, speech in New York, Oct. 22, 1928]Hoover said the phrase was not his own, and it is attested from 1897, though not in a patriotic context. Related: Ruggedly; ruggedness.