Jetsam is specifically goods thrown overboard on purpose — legally distinct from flotsam (accidental wreckage), and the difference determines who gets to keep what washes ashore.
Goods deliberately thrown overboard from a ship, especially to lighten the vessel during an emergency; unwanted or discarded material.
An alteration of earlier jetteson, from Anglo-Norman getteson, from Old French getaison (a throwing), from Latin iactātiōnem (a throwing, a tossing), accusative of iactātiō, from iactāre (to throw, to hurl), frequentative of iacere (to throw), from PIE *yeh₁- (to throw, to do). Key roots: *yeh₁- (Proto-Indo-European: "to throw, to do").
Jetsam and flotsam are not synonyms — they have precise legal differences that matter enormously in maritime law. Jetsam is deliberately thrown overboard (from jeter, to throw); flotsam is wreckage floating after a ship sinks (from floter, to float). The distinction determines who owns the goods