It goes back at least to Plutarch: https://penelope.uchicago.edu/misctracts/plutarchE.html https://penelope.uchicago.edu/misctracts/plutarchE.html There's spe

It goes back at least to Plutarch: https://penelope.uchicago.edu/misctracts/plutarchE.html https://penelope.uchicago.edu/misctracts/plutarchE.html There's speculation that this was derived from an earlier Erisian mystery cult, but how it ended up in a temple of Apollo I'm sure I don't know.