Etymology: < classical Latin Pȳthius (adjective) of or relating to Delphi, or to the oracle and priestess of Apollo at Delphi, (noun) Delphic Apollo ( < ancient Greek Πύθιος of Delphi, or the Delphic Apollo) + -an suffix. Compare Middle French, French pythien (1550).Ancient Greek Πύθιος is now generally held to have been derived from Πυθώ or Πύθων (classical Latin Pȳthō , Pȳthōn ), the older name of Delphi and the surrounding region; but it was in ancient times connected with the legend of the πύθων or monstrous snake said to have been slain there by Apollo (see python n.1).
Chiefly Greek Hist.
a. A native or inhabitant of Delphi. Freq. applied as a cognomen of Apollo (cf. Pythian Apollo n. at Special uses).
b. The priestess of Apollo at Delphi; = Pythia n. Also fig. and in extended use.
B. adj.Of or relating to Delphi or to the oracle or priestess of Apollo at Delphi. Also: of or relating to the Pythian games. (OED)
"A sort of suppressed terror hung in the air and seemed to seize us,—a pythian madness, a demoniac possession, that lent terrible reality to song and word."
- W.E.B. DuBois, The Souls of Black Folk, 1903