The first reference to the island's name is in an Arabic manuscript of the pirates' era (7th century), where the island is referred to as "Ashab al baqar", the "deer island", a name that is found again in nautical charts of the 16th century, where Elafonisos is called Isola di Cervi (Deer Island).
The ancient name of the island, when it was still connected to the mainland, was "Onou Gnathos", meaning "donkey' s jaw", because of its shape. Strabo, Pausanias, Ptolemy, Hesychos and, in modern times, Meletios (he names it "Onougnathon") and Korais are among those who mention this name.
A rare Arabic manuscript (No. 276 of the National Library of Paris), speaks of the "Ashab al baqar Castle" which Professor D. Goutas, Arabologue, translates as Castle of the "Deer Island" that was located in the Monemvasia region. The castle was destroyed in the 9th century by the Saracens.
The name "Elafonisi" (meaning “deer island”) is also mentioned by W. Leake, A. Bursian, and E. Curtins.
The etymology of the name "Elafonissi" verifies a local toponym (of a small settlement), with the analogous and odd name "Viglafia". During the Byzantine era, throughout the empire, there were the Vigles (or watchtowers) at a distance of 4 kilometers from each other. Of course in the area of Elafonisos the one Vigla was... at "Vigla". The other was about four kilometers away, at the most sensitive point of the island, in front of the Isthmus that was then passable, in Viglafia (Vigla + Lafia: in local dialect “lafi” stands for “elafi”, meaning “deer”).
A local legend that the residents narrate, especially the elderly, talks about a ship that was sailing in the area and was carrying deer and other animals. A female pregnant deer, fell into the sea, swam up to the island and gave birth there. In any case, the presence of deer in the area during the past is confirmed.
Names of the island
Cevre or Serbe: Venetian or Slavic name, which refers to the word "dew".
Lafounissia, Lafonisia: (also referred to by the Portolans - detailed local nautical maps) and
Elafonisia, Elafonisos: (due to the many islands and especially the many islets that existed previously in the current Isthmus of the island).
Elafonisi: (also referred to by W. Leake, A. Bursian, E. Curtins)
Alafonisi: (also referred to by Kolokotronis in his memoirs)
Lafonision
Lafonisi: mainly in the local dialect
Elafonisos: current official name
Sources
Mentis, K., 1994, S. Peloponnesus and its “smigopelaga” islands. - Il Peloponneso meridionale e le sue isole “smigopelaga”, Elafonisos: Library of Elafonisos/Bibliotheca di Elafonisos