Hi Peter.
Karenina?) It is possible that mathematicians actually reintroduced it after it had already been extinct. Perhaps Lambek is the culprit, or someone like Grothendieck, or even Girard.
Well, Girard is too young for this. Grothendieck rarely wrote in English. I will ask Lambek: it probably is something he remembered from his youth. Marcia (in her editor's r\^ole) considers it quite obsolete, and wonders why mathematicians use it... actually, one should trace the Latin route through French to English. I think the circumflex in the French denotes some missing letters from the Latin, but maybe that's not the correct etymology. Anyway, the English usage (in all the books we have here, including Fowler's and many dictionaries in French and English) definitely point to the sans-circumflex as the preferred spelling. But I'll try to find out more... Best, Phil