What is "sicinnus"

Sicinnus , a Persian according to Plutarch, was a slave of the Athenian leader Themistocles and pedagogue to his children. He is known for his actions as a negotiator between Themistocles and the Persian ruler Xerxes I during the Second Persian invasion of Greece. Sicinnus deceived Xerxes into sending his fleet into Themistocles' trap.