Thessalonike of Macedon was the daughter of king Philip II of Macedon, and sister to Alexander The Great.
We don’t know her exact date of birth but most historians seem to believe that she was born in 342 BCE.
Her name is made up of two Greek words, Thessaly and nike, which means “Thessalian Victory” and she was said to be thus called because, on the day of her birth, her father had won a significant battle against the Phoceans in Thessaly.
When he received the news of his child’s birth, he is said to have exclaimed “Let her be called Victory in Thessaly!”.
The myth states that Alexander the Great (Thessalonike’s brother), in his quest for the Fountain of Immortality, retrieved a flask of immortal water with which he bathed his sister’s hair.
When Alexander died his grief-stricken sister attempted to end her life by jumping into the sea. Instead of drowning, however, she became a mermaid.
As a mermaid, she lives in the Aegean and when she encounters a ship she asks its sailors only one question: “Is King Alexander alive?” (Greek: ”Ζει ο Βασιλιάς Αλέξανδρος;”), to which the correct answer is: “He lives and reigns and conquers the world” (Greek: “Ζει και βασιλεύει και τον κόσμο κυριεύει”). This answer pleased her so she calmed the waters and wished the ship farewell.
Any other answer would spur her into a rage, raising a terrible storm, dooming the ship and every sailor on board.