Skull and crossbones (symbol)

A skull and crossbones is a symbol consisting of a human skull and two long bones crossed together under the skull. The design originates in the Late Middle Ages as a symbol of death and especially as a memento mori on tombstones.

In modern contexts, it is generally used as a hazard symbol that warns of danger, usually in regard to poisonous substances, such as deadly chemicals.

Unicode uses U+2620 ☠ SKULL AND CROSSBONES (HTML ☠) for the symbol.

The symbol originates with the medieval Danse Macabre symbolism. By the 15th century, the symbol had developed into its familiar form. Since at least the 15th century it has been used in military flags or insignia, typically expressing the recklessness or ferocity of the unit displaying it, and has additionally become associated with piracy in the 18th century. It came to be used specifically to mark the entrances of Spanish cemeteries, and has been used to mark poison and other dangerous liquids and powders since the 19th century.

The skull and bones are often used in military insignia, e.g. in coats of arms of some military regiments.

In 1829, New York State required the labeling of all containers of poisonous substances. The skull and crossbones symbol appears to have been used for that purpose since the 1850s. Previously a variety of motifs had been used, including the Danish "+ + +" and drawings of skeletons.

In the 1870s poison manufacturers around the world began using bright cobalt bottles with a variety of raised bumps and designs (to enable easy recognition in the dark) to indicate poison, but by the 1880s the skull and cross bones had become ubiquitous, and the brightly coloured bottles lost their association.

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