The Valkyrie are Nordic Warrior Maidens who attend to Odin, the Father of the Gods, and determine the course of wars. Tall, blonde, and fair-skinned, the Valkyrie carry the souls of the bravest fallen warriors to their comfort in Valhalla, greeting them with horns of mead and serving them in pure white robes. The name of each of the Valkyrie reflects her specific quality or role.
"Rathgrith" means "Counsel of Peace," or "The Peace of the Gods." I find it ironic that one of the "Warrior Maidens" would be given the duty to advise peace. A pacifist warrior.
I consider myself a pacifist warrior. I believe strongly in fighting for the right causes (freedom, love, home, a decent cup of coffee), but I can not condone violence as a solution (unless the coffee is quite dreadful).
Thanks to mightyodinn and saint_sava, I believe that rathgrith is pronounced with the "a" sounding like the "ou" in "sound," the "i" sounding like "ee," and both of the "th"s sounding like the "th" in "these," with the emphasis on the first syllable. You can see how I came to this belief here.
I recently found more information: "If anyone's played Ace Combat 5 or is familiar with Norse Mythology, then you've heard of Razgriz/Rathgrith. In AC5 (Razgriz, a play on the name Rathgrith for game purposes) she is said to be a demon responsible for great destruction followed by her angelic form that brings peace or salvation. In the Norse Mythos she (Rathgrith) is a warrior of peace."