Indian potato

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various North American plants that produce edible tubers, such as groundnut and spring beauty (Claytonia virginica).
• noun One of the starchy, edible tubers produced by these plants, traditionally eaten by Native American peoples.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of several kinds of North American plants with edible, starchy bulbs or other underground structures, such as mariposa lilies, groundnuts, etc.