The MythMan has this story, which may explain the origin of Pallas.

Athena's favorite companion when she was a child was a girl called Pallas, and the two were inseparable, honing their fighting skills and sharing good times. One time, during a practice sparring session, Athena accidentally mortally wounded her best friend, and grieving sorely for her death, Athena made a wooden image in her likeness, which was called the Palladium. She also took on her name as part of hers and henceforth was often referred to as Pallas Athena.

Carlos Parada at the Greek Mythology Link has these details:

Athena was reared by Triton (the son of Poseidon and Amphitrite) together with his own daughter Pallas 3. The two girls, they say, were playmates, and once, as they were practising the arts of war and Pallas 3 was about to strike a blow, Zeus, fearing for his daughter, interposed the aegis to protect Athena; and when Pallas 3, being caught by surprise, looked up, Athena hit her, and she fell wounded and died.

Athena makes the image In order to calm her grief, Athena made a three cubits high wooden statue in the likeness of Pallas 3, with the feet joined together, and holding in its right hand a spear, and in the left a distaff and spindle. And wrapping about its breast the aegis that had frightened her friend, she set the image up beside Zeus, and honoured it in Heaven.

As such, perhaps Pallas can be considered the goddess of the Martial Arts.

In Italian, Armata means armed.