In 1784, a lieutenant in the British Army named Henry Shrapnel invented a new kind of cannonball filled with little lead parts that went everywhere when the ammunition exploded. He demonstrated it in Gibraltar, and it became so popular that the Army adopted it in 1803. Henry meant for the shell type to be called spherical case ammunition, but that was a mouthful, so people just used his last name for it, and that rapidly got extended to refer to fragmentation from shells like his. By 1810, someone decided it was an uncountable noun, so we got stuck with the plural shrapnel instead of shrapnels, and usage peaked in World War I. It's believed that the surname shrapnel comes from French Charbonnel, the root being charbon, their word for "charcoal" (a reference to hair color).
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.