Cool spice Kokum (also spelled kokam) is the "round purple fruit the size of a small orange" produced by the Garcinia indica tree, according to The Oxford Companion to Food. But unless you visit the parts of India where it grows, you're unlikely to see fresh specimens.
Elsewhere, you'll find the dried version - either as a shrivelled whole fruit or ground into a coarse powder. It has a tart, fruity and acidic flavour, and cooling qualities, and is often used to make drinks. It's also used medicinally to treat inflammation, digestive problems and allergies.
Regency Spices (regencyspices.hk), an online spice shop that sells kokum, says, "A recent pharmaceutical study found that kokum extract decreases anxiety levels in mice, and may hold the same effect for humans, too. Commercial research to find other health and skin benefits have also proven successful."
The site advises using kokum for "dals, soups, vegetable and fish stews, and other liquid-heavy dishes", adding that one whole fruit should be added at the beginning of a long-simmered dish, "to impart a lovely fruity, herbal and sour flavour".