Truffle, e.g

• A common European plant having edible tubers with the flavor of roasted chestnuts
• Grow naturally in southwestern Europe
• Truffle, e.g.
• Pod of the peanut vine containing usually 2 nuts or seeds
• Any of various highly prized edible subterranean fungi of the genus Tuber
• Edible subterranean fungus of the genus Tuber

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Groundnut \Ground"nut`\ (ground"n[u^]t`), n. (Bot.) The fruit of the Arachis hypog[ae]a (native country uncertain); the peanut; the earthnut. A leguminous, twining plant ( Apios tuberosa ), producing clusters of dark purple flowers and having a root tuberous ...

Wikipedia Word definitions in Wikipedia
Earthnut is a common name for several unrelated plants which produce a subterranean edible seed, fruit or root Earthnut may refer to: Truffle Peanut Roots and tubers: Lathyrus tuberosus Conopodium majus Bunium persicum