In maritime lingo, flotsam is wreckage or cargo that remains afloat after a ship has sunk, and jetsam is cargo or equipment thrown overboard from a ship in distress. The precise meanings are lost in the common phrase flotsam and jetsam, which describes useless or discarded objects. The phrase is sometimes used to describe items floating or washed ashore, but it has also been extended into metaphorical use for any accumulation of odds and ends.
The two words most often appear together, as in these instances:
[T]here are thousands upon thousands of dissatisfied, disenfranchised people like her, the flotsam and jetsam on China’s rising tide of prosperity. [NPR]
It contains plastic flotsam and jetsam—toys, cups, wrappers, and bottles—that slowly degrade. [Christian Science Monitor]
[M]any Taningia specimens were recovered from the digestive flotsam and jetsam of these animals. [Wired]
They do occasionally appear separately, though flotsam is about ten times more common. Used alone, flotsam rarely retains its original meaning; it’s usually just a shortened form of the metaphorical flotsam and jetsam—for example:
But the essence of the story gets a bit lost amid a lot of verbal flotsam. [Australian]
The sand is charcoal-colored, driftwood and other flotsam makes a barefoot stroll unwise. [San Francisco Chronicle]