The real story
Thong sandals are ancient, but the cheap rubber flip-flop took off after World War II, modelled on the Japanese zōri, a flat sandal with a strap between the toes. In 1962 Brazil's Havaianas launched its rubber version, and the design spread across the tropics because it is cheap, waterproof and slips off in a second.
That last part matters in Indonesia, where you take off your footwear before entering a mosque, a prayer room or someone's home. After Friday prayers, rows of nearly identical blue-and-white sandals turn into a puzzle, and people mark theirs with initials, a notch in the sole or a mismatched strap so the right pair makes it home.
