Pyrrhic has multiple possible references, however the most likely is Pyrrhichios, an ancient dance performed by the Korybantes.
The Korybantes (Ancient Greek: Κορύβαντες) were the crested dancers who worshipped the Phrygian goddess Cybele with drumming and dancing. These male dancers in armor, kept time to a drum and the rhythmic stamping of their feet. Dance, according to Greek thought, was one of the civilizing activities, like wine-making or music. The dance in armor (the "Pyrrhic dance" or Pyrriche (Πυρρίχη)) was a male coming-of-age initiation ritual linked to a warrior victory celebration.
In a literal sense, 'Pyrrhic Kleos' would refer to glory (or fame) obtained at a great sacrificial price.