The story
Named after Prince Rupert of the Rhine, nephew of Charles I, who brought them to England in 1660.
Etymology from Wiktionary, CC BY-SA 4.0.
Rupert's drop
Today it means: A glass bead created by dripping molten glass into cold water so it solidifies into a tadpole shape with a very tough head but a long fragile tail which, if damaged, causes the bead to disintegrate explosively. Full definition →