Meaning: a Greek name meaning "flame-colored" or "red" from Greek element pyr (fire).
In Greek mythology, Achilles hid as a woman at the court of Lycomedes (or his mother Thetis hid him there) to prevent him from joining the Trojan war. Since the war could not be won without the aid of Achilles, Odysseus disguised himself as a peddler selling women's jewelry and clothes along with a spear and a shield. When Achilles picked up the weapons of war, that's how Odyseeus picked him out.
Another version of the tale goes that Odysseus arranged for an alarm to be sounded, so when the women fled in panic and Achilles stayed behind to fight, he was found out. He took the name Pyrrha when he was hiding out; his son Neoptolemus by Deidamia, a daughter of Lycomedes, was also called Pyrrhus, likely after his father's alter ego.