What is the X in X-mas?
1885 (usually in phrase Pyrrhic victory), from Pyrrhus, king of Epirus, who defeated Roman armies at Asculum, 280 B.C.E., but at such cost to his own troops that he was unable to follow up and attack Rome itself, and is said to have remarked, "one more such victory and we are lost."
"dance in armor" (1590s), also a type of metrical foot (1620s), from Latin pyrrhicha, from Greek pyrrikhe orkhesis, the war-dance of ancient Greece, traditionally named for its inventor, Pyrrikhos. The name means "reddish," from pyrros "flame-colored," from pyr "fire" (see fire (n.)). As an adjective from 1749.