E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A festival observed by the Persians to commemorate the massacre of the Magi. Smerdis usurped the throne on the death of Cambyses; but seven Persians, conspiring together, slew Smerdis and his brother; whereupon the people put all the Magi to the sword, and elected Darius, son of Hystaspes, to the throne. (Greek, magosphonos, the magi-slaughter.)