Ginkgo is so often misspelled as gingko (including by me) that the Oxford English Dictionary now accepts the spelling variation.
According to the Oxford Companion to Food, "Ginkgo biloba is the sole survivor of a group of primitive trees." A living fossil, the trees you find now are almost the same as the fossilised specimens that date back to the Jurassic era.
The ginkgo "nut" is actually the kernel of the ginkgo fruit, which has a lingering, extremely pungent and disgusting odour often compared with that of dog excrement or rotting flesh. When sold in markets (they're in season now), the kernels, with their thin, brittle shells, have been cleaned of the smelly, pulpy exterior, which can irritate the skin.
As delicious as they are, you shouldn't eat too many ginkgo nuts, nor should you consume them raw. According to the Hong Kong Centre for Food Safety, ginkgo contains a number of plant toxins, including cyanogenic glycosides and 4-methoxypyri-dine (4'MPN).
"Ginkgo seeds have dangerous poisoning effects due to the presence of toxins that are mainly neurotoxic," the centre says. "Children are especially susceptible to this type of food poisoning.
"In severe cases, where large amounts have been taken or in susceptible individuals, loss of consciousness and deaths may occur. Unripe and uncooked seeds are reported to be more toxic."