from The Century Dictionary and Cyclopedia
- n. In mathematics, a certain curve, ‘the witch of Agnesi.’ See witch.
Sorry, no etymologies found.
The plane curve, known as versiera, is also called "the Witch of Agnesi".
Somehow the English translator managed to read la versiera as l'avversiera - a she-devil.
It was originally named by the Italian mathematician Maria Gaetana Agnesi, who called it la versiera, apparently a nautical term meaning "a rope which turns a sail".