late 14c., "clearly revealed," from Old French manifest "evident, palpable," (12c.), or directly from Latin manifestus "plainly apprehensible, clear, apparent, evident;" of offenses, "proved by direct evidence;" of offenders, "caught in the act," probably from manus "hand" (see manual) + -festus "struck" (cf. second element of infest).
Other nations have tried to check ... the fulfillment of our manifest destiny to overspread the Continent allotted by Providence for the free development of our yearly multiplying millions. [John O'Sullivan (1813-1895), "U.S. Magazine & Democratic Review," July 1845]The phrase apparently is O'Sullivan's coinage; the notion is as old as the republic.
late 14c., "to spread" (one's fame), "to show plainly," from manifest (adj.) or else from Latin manifestare "to discover, disclose, betray" (see manifest (adj.)). Meaning "to display by actions" is from 1560s; reflective sense, of diseases, etc., "to reveal as in operation" is from 1808. Related: Manifested; manifesting.