Paian, Paieon, or Paion is a title of Apollo as the god of healing; various forms of this exclamation occur as refrains in choral songs addressed to Apollo or Artemis; cf. generally pi 836, pi 837, pi 838, pi 841, pi 842. See also alpha 1059, alpha 1062.
[1] From the scholia to Aristophanes, Birds 1763 (web address 1), where the headword phrase occurs. Compare Lysistrata 1291. Similar refrains occur in the Homeric Hymn to Apollo, 517; Aeschylus, Agamemnon 146; Sophocles, Oedipus Tyrannus 154; Aristophanes, Acharnians 1212.