From Africa, according to Herodotus, came Neptune, from the Pelasgi the rest of the deities disclaimed by Egypt.

According to the same authority, the Pelasgi learned not their deities, but the names of their deities (and those at a later period), from the Egyptians [24].

But the Pelasgi were the first known inhabitants of Greece--the first known inhabitants of Greece had therefore their especial deities, before any communication with Egypt.
For the rest we must accept the account of the simple and credulous Herodotus with considerable caution and reserve.

Nothing is more natural--perhaps more certain--than that every tribe [25], even of utter savages, will invent some deities of their own; and as these deities will as naturally be taken from external objects, common to all mankind, such as the sun or the moon, the waters or the earth, and honoured with attributes formed from passions and impressions no less universal;--so the deities of every tribe will have something kindred to each other, though the tribes themselves may never have come into contact or communication.
The mythology of the early Greeks may perhaps be derived from the following principal sources:--First, the worship of natural objects;-- and of divinities so formed, the most unequivocally national will obviously be those most associated with their mode of life and the influences of their climate.

When the savage first intrusts the seed to the bosom of the earth--when, through a strange and unaccountable process, he beholds what he buried in one season spring forth the harvest of the next--the EARTH itself, the mysterious garner, the benign, but sometimes the capricious reproducer of the treasures committed to its charge--becomes the object of the wonder, the hope, and the fear, which are the natural origin of adoration and prayer.
Again, when he discovers the influence of the heaven upon the growth of his labour--when, taught by experience, he acknowledges its power to blast or to mellow--then, by the same process of ideas, the HEAVEN also assumes the character of divinity, and becomes a new agent, whose wrath is to be propitiated, whose favour is to be won.