Nephrolepis cordifolia

sword fern

Natives in the Indian mountains cook and eat young leaves and also use the plant medicinally as a diuretic and in treating liver disorders. A scientific study of an extract of the rhizome of this plant was found to significantly increase urine output in rats, lending credence to the traditional use. In Nepal, juices from underground parts of the plant are used to treat indigestion, fever, cold, and cough.

This fern produces globular underground tubers that are edible raw or roasted for nutrition and hydration (their primary function for the plant is water storage). They are commonly eaten in Nepal and are apparently not that bad. Here's a good little video about harvesting and eating the tubers:

In Hawaii, fronds of the fern have been used for many generations as lei for the wrists, ankles, and head.