Jerusalem artichoke

noun
1.
Also called girasol. a sunflower, Helianthus tuberosus, having edible, tuberous, underground stems or rootstocks.
2.
Also called sunchoke. the tuber itself.
Origin
1635-45; alteration of Italian girasole articiocco edible sunflower. See girasol, artichoke
British Dictionary definitions for Jerusalem artichoke

Jerusalem artichoke

noun
1.
a North American sunflower, Helianthus tuberosus, widely cultivated for its underground edible tubers
2.
the tuber of this plant, which is cooked and eaten as a vegetable
See also artichoke (sense 1), artichoke (sense 2)
Word Origin
C17: by folk etymology from Italian girasole articiocco; see girasol