When the Phoenicians conquered the island the name was changed to Kalisti
(the very best).Later on the name was change to Thera in honour of king Thera of Sparta. The Romans used Thera as place to send exiles.
Sometime between the 2th and the 5th century, Christianity was introduced to the island.
Pirates attacked the island numerous times.
The Venetians came in 1204 and conquered. It was then it took the name for which it is known today.The patron saint was Agia Irini and the sailors called Santa Irini.
Thus the name Santorini.
In 1354 and 1397 the island was destroyed by the Venetians.