Fiddlehead refers to the unfurled fronds of a young fern harvested for food consumption. The fiddlehead unrolls as the fern matures and grows due to more growth in the inside of the curl. Fiddleheads are usually located by the bottom of a fern plant.
Fiddleheads resemble the curled ornamentation (called a scroll) on the end of a stringed instrument, such as a fiddle. It is also called a crozier, after the curved staff used by shepherds and bishops.
The fiddleheads of certain ferns are eaten as a cooked leaf vegetable. They must be cooked first to remove shikimic acid.
For more information on fiddlehead ferns visit Wikipedia.