One afternoon, 1965, the three Louisianan sisters/cousins who gave you “Chapel of Love,” unaware that the studio’s tapes were still rolling, recorded for posterity two minutes of delightful historical intrigue that had been circulating in oral obscurity for generations unknowable. “Iko, Iko,” they called that tune. The English chunks of the record came from an all-too-obvious source—R&B singer “Sugar Boy” Crawford who claimed he never saw “just dues” from the top 40 hit—but the cryptic re...