Pluto (Greek Plouton) is a deliberately propitiatory name for the ruler of the dead, connected with ploutos, wealth, the riches of metals and, above all, the grain that springs from beneath the ground. Greeks were reluctant to name Hades directly, and Plouton let them address the god of the underworld as a giver rather than only a terror. The name rose to prominence through the Eleusinian Mysteries, where the lord of the dead appeared not as an abductor but as a solemn consort of Persephone and a source of the earth's abundance, sometimes shown holding a cornucopia. This is the positive face of the underworld god, and it is the reason a deity of death carries a name meaning wealth.
Pluto is regularly shown in later Greek and Roman art holding a large key as well as the cornucopia, the key that locks the gates of the dead and ensures none return without his leave, a darker attribute balancing the abundance suggested by the horn of plenty. A handful of actual cult sites called Ploutonia, sanctuaries built around openings believed to lead to the underworld, are known archaeologically, the most famous at Hierapolis in Asia Minor, where the geographer Strabo describes a cave that killed any animal driven into it by toxic vapour, a site excavated and confirmed in 2013 to emit lethal volcanic carbon dioxide; ancient priests of Cybele reportedly entered and survived, an effect modern researchers attribute to holding their breath rather than divine favour.