"of or pertaining to King Pyrrhus of Epirus," 1885, usually in the phrase Pyrrhic victory "success obtained at too great a cost," in reference to Pyrrhus's rout of Roman armies at Asculum, in Apulia, 279 B.C.E., which came 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." The name is Greek and means "reddish" or "red-haired," from pyrrhos "flame-colored," from pyr "fire" (from PIE root *paewr- "fire").
"dance in armor" (1590s), also a type of metrical foot of two short syllables (1620s), from Latin pyrrhicha, from Greek pyrrikhē orkhēsis, the war-dance of ancient Greece, in quick and light measure, accompanied by the flute, traditionally named for its inventor, Pyrrikhos. The name means "reddish, red-haired," from pyrrhos "flame-colored," from pyr "fire" (from PIE root *paewr- "fire"). As an adjective, "of or pertaining to the pyrrhic," from 1749.