This plane algebraic curve was named by Maria Agnesi in 1748 although it had been investigated earlier by Fermat.

An equation for the curve is given by y(x2 + a2) = a3, for a constant real number a.

Apparently the name of witch coming from the Italian versiera arises because Agnesi confused two different Italian words. Disappointingly, the curve has no supernatural properties. But if it worries you I suggest throwing it in some water and seeing if it floats.

Historical info sourced from