Spiny dye-murex Snail

From Wikipedia:

The modern English word purple comes from the Old English purpul, which derives from Latin purpura, which, in turn, derives from the Greek πορφύρα (porphura), the name of the Tyrian purple dye manufactured in classical antiquity from a mucus secreted by the spiny dye-murex snail. The first recorded use of the word purple dates to the late 900s AD.