1580s, name of a fabled serpent, slain by Apollo near Delphi, from Latin Python, from Greek Pythōn "serpent slain by Apollo," probably related to Pythō, the old name of Delphi. Chaucer has it (late 14c.) as Phitoun.
This might be related to pythein "to rot," or from PIE *dhubh-(o)n-, from *dheub- "hollow, deep, bottom, depths," and used in reference to the monsters who inhabit them. Loosely used for "any very large snake," hence the zoological application to large non-venomous snakes of the tropics (1836, originally in French). Related: Pythonic.
"priestess of Apollo at Delphi," who received his oracles in the inner sanctuary of the great temple, 1842, from Greek pythia (hiereia) "(Priestess) of Pythian Apollo," from a variant form of Pythios, an epithet of Apollo, from Pytho, older name of the region of Delphi (see python).
late 14c., phitonesse, Phitonissa, "woman with the power of soothsaying," from Old French phitonise (13c.) and Medieval Latin phitonissa, from Late Latin pythonissa, used in Vulgate of the Witch of Endor (I Samuel xxviii.7), and often treated as her proper name. It is the fem. of pytho "familiar spirit;" which ultimately is connected with the title of the prophetess of the Delphic Oracle, Greek pythia hiereia, from Pythios, an epithet of Apollo, from Pythō, an older name of the region of Delphi (see python). The classical spelling was restored 16c.
1975, in reference to the style of humor popularized by the comedy troupe in the British TV series "Monty Python's Flying Circus."