Meaning: a Greek feminine name meaning "hidden, forgotten" or "oblivion" from Greek lethe, though it's also been associated with Lycian lada meaning "woman" and "lady".
Leto is also a surname, perhaps the Italian form of Latin Laetus perhaps meaning "happy"
In Greek mythology, Leto was the mother of twins Apollo and Artemis by Zeus. When Hera found out she was pregnant with his children, she constantly pursued her from land to land, preventing her from giving birth. Leto eventually found refuge on the floating island of Delos and gave birth to first Artemis and than Apollo.
In Roman mythology, her counterpart is Latona.
Although Leto is traditionally a feminine name, it has been used as a male name in Frank Herbert's Dune books, belonging to the main character's father and his sons.