c. 1400, desperat, of persons, "despairing, hopeless" (a sense now obsolete), from Latin desperatus "given up, despaired of," past participle of desperare "to despair, to lose all hope," from de "without" (see de-) + sperare "to hope," from spes "hope" (from PIE root *spes- "prosperity;" see speed (n.)).
Of persons, "without care for safety, extremely rash, driven to recklessness by despair," from late 15c.; weakened sense of "having a great desire for" is from 1950s. Of conditions, "extremely serious," from 1550s. Of actions, "done or resorted to without regard for consequences," 1570s. Related: Desperately; desperateness.