Zeus, being Zeus went after the Titaness Leto, finding her to be more lenient and compliant than her sister Asteria, who ran from Zeus. Leto was eventually pregnant with twins, but once Hera found out, she was furious, she decided to make Leto's pregnancy as painful as possible, because why the hell not.
Hera enlisted the help of Ares and Iris, and they made sure that Leto could not receive refuge anywhere on earth. And so Leto was forced from mainland Greece by a massive Python, and anywhere she went, she had to leave as it was earth.
She eventually sought refuge on the floating island Ortygia; which was once her sister Asteria, who transformed herself into it to hide from Zeus. Being unattached to the earth, Leto was free to stay there, away from Hera's wrath, because Hera respected Asteria for having not given in to Zeus.
And right by a lake there on Ortygia, Leto endured painful labour, until she eventually gave birth to Artemis, who would grow to be worshipped as Goddess of Wild Beasts and the Hunt, along with Midwifery.
And because she was divine, as soon as she was born, she was helping her mother deliver her brother, Apollo, god of light.
But because Hera was a raging bitch, as soon as the birds and the nymphs sang of the childbirth, she was furious, and so at that moment, the island's bedrock turned to gold, the lake flowed with gold, the leaves were gold, and the island was now anchored to the ocean, and was known from then on as Delos ('clearly seen').