THE NESOI were the goddesses of the islands. Each island was said to have its own personification. They were numbered amongst the ancient elemental gods called Protogenoi. According to Callimachus the Nesoi (Islands) were Ourea (Mountains) cast into the sea by Poseidon with his trident.

Callimachus, Hymn 4 to Delos 15 ff (trans. Mair) (Greek poet C3rd B.C.) :
"But none need grudge that she be named among the first, whensoever unto Okeanos and unto Titanide Tethys the islands gather and she [Delos] ever leads the way. Behind her footsteps follow Phoinikian Kyrnos, no mean isle, and Abantian Makris of the Ellopians, and delectable Sardo, and the isle whereto Kypris first swam from the water [Kypros] and which for fee of her landing she keeps safe. They are strong by reason of sheltering towers, but Delos is strong by aid of Apollon. What defence is there more steadfast? Walls and stones may fall before the blast of Strymonian Boreas; but a god is unshaken for ever. Delos beloved, such is the champion that encompasses thee about! . . . The tale how at the very first the mighty god [Poseidon] smote the Mountains (Ourea) with the three-forked sword which the Tekhines fashioned for him, and wrought the islands in the sea, and from their lowest foundations lifted them all as with a lever and rolled them into the sea? And them in the depths he rooted from their foundations that they might forget the mainland. But no constraint afflicted thee, but free upon the open sea thou didst float; and thy name of old was Asterie, since like a star thou didst leap from heaven into the deep moat, fleeing wedlock with Zeus."

Callimachus, Hymn 4 to Delos 153 ff :
"After much toil She [Leto pregnant with Apollon and Artemis and forced to wander the earth by the rage of Hera] came unto the Isles (Nesoi) of the sea. But they received her not when she came--not the Ekhinades with their smooth anchorage for ships, not Kerkyra which is of all other islands most hospitable, since Iris on lofty Mimas was wroth with them all and utterly prevented them. And at her rebuke they fled all together, every one that she came to, along the waters. Then she came unto primeval Kos, the isle of Merops, the holy retreat of the heroine Khakliope, but the word of her son [Apollon in the womb] restrained her : `Bear me not, mother, here. I blame not the island nor have any grudge, since a bright isle it is and rich in pasture as any other. But there is due to her from the Moirai (Fates) another god.'"

Philostratus the Younger, Imagines 1 (trans. Fairbanks) (Greek rhetorician C3rd A.D.) :
"The heroine crowned with reeds--for doubtless you see the female figure at the foot of the mountain, sturdy of form and dressed in blue--is the island of Skyros, my boy, which the divine Sophokles calls 'wind-swept.' She has a branch of olive in her hands and a spray of vine."

Sources:

• Callimachus, Hymns - Greek Poetry C3rd B.C.
• Philostratus the Younger, Imagines - Greek Rhetoric C3rd A.D.