It's the Spartan lambda, and it stands for "Lacadaemon", which was the official name of Sparta. Now, you probably wonder how that embodies what you've asked, and I'll tell you how.
Strength: The Spartans were the roughest, toughest, most skilled warriors in all of the ancient world. Obesity and poor fitness were frowned upon, and every Spartan male was forced to enter a rigorous training program called the "agoge" when he was seven years old. During this time, they would be deprived of foodfor certain periods of time, forced to live in the wilderness, and would only be given one tunic and a pair of sandals to wear for the year. One typical training "game" consisted of several Spartan boys being tied to a stake with each boy being whipped until he forfieted the game; the winner was the last man standing. Some even died from this game--refusing to forfeit and be called a coward or weakling,
Boldness: The Spartans were well-known for their famous bravery; a Spartan could never retreat from battle. It was bound by law. Spartan mothers would routinely tell their sons to "come back with their shields or upon them". This meant tthat the Spartan son must either come back victorious--or dead. There was no other choice.
Confidence: Spartans were also known for their quick wit. Even in the face of mortal peril, the self-assured Spartans would taunt their enemies. So confident of their combat ability, at the Battle of Thermopoylae, when the Spartans and their allies were ounumbered by a Persian force 50-to-1, King Leonidas of the Spartan called at the Persian forces come and try to take their weapons. When Macedonian King Philip, who's military forces also heavily outnumbered the Spartans, declared that he would raze Sparta to the ground if it didn't surrender, the Spartans only invited him to try an invade. In terms of confidence, no one beats Spartans.
Femininity: While this might not be as well-known, Spartan women enjoyed far greater liberties than most any other women in the anicent world. They could own property, be seen in public, adn exercise with their male counterparts. Like the male agoge, females were trained to be physically-fit, fertile, and battle-hardened. Hell, ther are even accounts of women fighting with the Spartan men on the battlefied. When asked why women enjoyed so many liberties in Sparta, their Queen Gorgo responed "because only Spartan women give birth to real men". That's strong femininity if I've ever heard it.