I recently ran across the Russian expression локон Аньези ‘curl of Agnesi’ and wondered “Why do we call it ‘witch of Agnesi’?” So I googled and found this explanation at Wikipedia:
It gets its name from Italian mathematician Maria Gaetana Agnesi who published it in 1748. The Italian name la versiera di Agnesi is based on Latin versoria (sheet of sailing ships) and the sinus versus. This was read by John Colson as l’avversiera di Agnesi, where avversiera is translated as “woman who is against God” and interpreted as “witch”.
That’s quite a story, but I’m not sure about the “read as avversiera” part, because apparently Italian versiera can mean ‘witch, she-devil,’ so there’s no need to charge poor Colson with misreading, just misunderstanding. The OED, s.v. witch (revised 2021), has:
II.8. Mathematics. More fully witch of Agnesi. A bell-shaped plane curve symmetrical about the y axis and that approaches the x axis as an asymptote, constructed geometrically from a circle whose base is the origin.
The first citation is Colson:
a1760 The equation of the curve to be described, which is vulgarly called the Witch [Italian che dicesi la Versiera].
J. Colson, translation of M. G. Agnesi, Analytical Inst. (1801) vol. I. i. v. 222
And under Etymology:
In sense II.8 representing a mistranslation (in quot. a1760) of Italian †versiera, denoting a curve based on a versed sine (1718, introduced by G. Grandi as an Italian equivalent for his post-classical Latin versoria: see versor n.²), by association with versiera female demon (15th cent; ultimately related to avversario adversary, devil: see adversary n.); in witch of Agnesi with reference to the name of Maria Gaetana Agnesi (1718–99), the author of the work translated in quot. a1760.
There is Russian expression локон Аньези, but less romantic name of the same is верзиера (versiera) which, TIL, is a particular case of аньезиана (agnesiana). And reading Wiki article on the latter I came to a remarkable sentence: В декартовых координатах аньезиана — это гиперболизм окружности followed by a reverse of it Образующая окружность есть антигиперболизм аньезианы.
Wow, those are wonderful sentences, and аньезиана is a wonderful word.