Today the name Spinalonga is only applied to the islet, but the Venetians used it to include the large peninsula of Nissi or Kolokytha, which is connected to Elounda by a narrow isthmus.
Apparently Kolokytha used to be joined to Spinalonga (which is why it shared the same name), but in 1526 the Venetians cut a canal between the two, forming this small island.
This information comes from the Venetian cartographer Vincenzo Coronelli, but it may not be true. However, the islet is only 170 metres from Kolokytha and the water is shallow, so perhaps the Venetians did indeed carry out this project to form an impregnable island fortress.
The name Spinalonga appeared around the 13th century, bestowed by the Venetian conquerors, who, unfamiliar with Greek, corrupted the place-name “Stin Olounda” (“at Olounda”), originally to Spinalonde (13th century) and later to Spinalonga. It is no coincidence that the small island of Giudecca near Venice was also known as Spinalonga.
According to another interpretation the name of the island is derived from its shape, like a long thorn (spina longa), but this theory is not widely held.
Much later, in 1957, another name, Kalydon, was proposed for the island, in an unsuccessful attempt to replace the Latinate Spinalonga with a Greek name.