There is no record that the Greek island Mathraki was inhabited in the ancient or the Medieval times. The long distance from mainland Greece and the piracy, which was much active in the Greek seas till the mid 19th century, prevented people from residing in Mathraki.
In fact, the three Greek islands of the Diapontia complex (Mathraki, Othoni and Ereikoussa) were not inhabited till two centuries ago and were used only as middle stops in long sea voyages.
It is recorded that the first of three islands to be inhabited was Othoni. People from Corfu and from the mainland coasts of Parga started to live in Othoni to get away from the Ottoman rule.
At the end of the 19th century, the inhabitants of Othoni went to the close islands of Mathraki and Ereikoussa to cultivate the vast groves of olive trees. Along time, people started to live permanently in Mathraki and built houses there.
This is how Mathraki eventually got inhabited. Today, it is still an isolate island whose inhabitants are limited to the basic comforts.