In 1986, DC Comics had over two dozen parallel universes and a wacky continuity. So they did a maxi-series called "Crisis on Infinite Earths", where all Earths (and their universes) were merged into a single universe, their histories mixed together.
In the wake of Crisis, DC did a reboot on its major characters, starting with Superman (in the Man of Steel mini-series by John Byrne), then Batman (Year One, by Miller and Mazzuchelli) and finally Wonder Woman (by George Perez). This last one brought WW back to her mythological greek roots.
The Greek Godesses (plus Hermes) gave new bodies to the spirits of women slain by the cruelty of men, creating the Amazons. The Amazon's hubris caused their downfall and slavery at the hands of Herakles (Hercules). After their escape, the Amazons were guided to the island of Themiscyra, where they would be ageless, but they'd have to stand watch at the Gate of Doom, underneath the island. Many Amazons died that way.
Flash-forward some 2000 years.
A test plane piloted by one of the first women pilots ever, Diana Trevor, falls in Themiscyra. Diana gets involved into a battle with one of the demons trying to escape through the Gate of Doom, and dies. The Amazons build a mausoleum in her honor, and fashion an armor based on the heraldry Diana Trevor displayed (the US Air Force badge). They also kept her sidearm, which was to be used in a test to identity a prophesised warrior.
Flash-forward another 30 years.
Hippolyta, queen of the Amazons, feels a strange yearning. She finds out that in her previous life she was pregnant when she was slain, so now her body yearns to give birth. The goddesses bid her sculpt a baby girl's body in clay and into that body the send the last of the slain women's spirit, the spirit of Hyppolita's unborn daughter. The clay body becomes flesh and the girls comes alive. Hippolyta honors Diana Trevor by calling her daughter Diana.
Unknown to Hyppolita, as they sent the spirit into the clay body, the goddesses (plus Hermes) grant her powers: Wisdom (Athena), Strength (Demeter), Communion with Animals (Artemis), Truthfulness (Hestia), Beauty (Aphrodite) and Flight (Hermes). They did this because they knew a conflict with Ares, the war god, was coming.
When she was around 22, Diana secretly competed in a contest held to find a champion that was to be sent to Patriarch's World (i.e. outside Themiscyra) to battle the growing influence of Ares (this was published during the Cold War). No matter how fast, strong or skilled the other Amazons were, Diana won every match. Despite Hyppolita's protests, Diana was named champion.
She was outfitted with the armor inspired by Diana Trevor's heraldry, and won also unbreakable bracers. She was then tested by being fired upon point-blank with Diana Trevor's .45 gun, which she deflected with the bracers.
The goddesses sent to her a weapon, a lasso forged by Hephaestos out of Gaea's Girdle, a weapon of Truth.
When she came to Patriarch's World, she was dubbed Wonder Woman, after a heroine of WWII.
The Wonder Woman of WWII was in fact the Hippolyta of the near-future, where Diana was to be killed by the demon Neron, and subsequently elevated to the status of Goddess of Truth. During her short stint as Wonder Woman, Hyppolita went back in time to World War II and became a member of the Justice Society of America. Hippolita had almost no powers, but wore the bracer of Atlas for superstrength, the sandals of Hermes for flight and speed, and had acquired a transparent alien substance that could be fashioned mentally into any vehicle she could imagine. This was to be known as the Invisible Plane (which inspired the young Diana Trevor to join the Air Force in the first place).
Hippolyta has since returned to the present and recently died during a universe-spanning battle against the being Imperiex.