means Fragments of metal scattered by an exploding bomb, shell, or mine — and, loosely, any small bits of loose change rattling in your pocket.

from A genuine eponym: it comes from Henry Shrapnel, a British artillery officer who in the early 19th century devised a hollow shell packed with lead balls and a bursting charge, designed to scatter shot over advancing troops. His name attached first to the 'Shrapnel shell,' then to the deadly fragments themselves. Over time the meaning drifted from the man's purpose-built projectiles to any jagged splinters thrown off by an explosion — and, jokingly, to the coins jingling at the bottom of a bag.