I'm afraid Alexey's conjecture about "chose" and Les Fleurs du Mal seems most unlikely; “chose” is as common in French as “thing” in English or “veshch'” in Russian and could be found in other texts in more or less close proximity to Aqua (such as A la Recherche du temps perdu).

I offer from my Annotations to ADA one likely, but perhaps incomplete, explanation, and one unlikely, that nevertheless involves “Chose” as (albeit temporarily) the name for a town.

ššššššššššš 18.24: Chose: This proves to be Antiterran for Cambridge, England, although the reason remains unclear. Perhaps because of the expression "Hobson's choice," from the practice of Thomas Hobson (1544-1631), the famous "university carrier" at Cambridge, who when he hired out horses made each customer "choose" the horse nearest the door. Milton wrote two poems on the death of Hobson, whose name--as Nabokov would have known from his years there as a student (1919-22)--is commemorated around Cambridge in, for instance, Hobson's Conduit and Hobson's Brook (also known as the Cambridge New River).

ššššššššššš Though this seems an even less likely connection, I note it anyway, since it shows "Chose" playing, even if briefly, the part of a town's name. In Villette (1853), by Charlotte Bronte (1816-55), narrator Lucy Snowe hears Ginevra Fanshawe declare: "`I was excessively happy at Bonn!' `And where are you now?' I inquired.//`Oh! at - chose,' said she. Now Miss Ginevra Fanshawe (such was this young person's name) only substituted this word `chose' in temporary oblivion of the real name. It was a habit she had: `chose' came in at every turn in her conversation - the convenient substitute for any missing word in any language she might chance at the time to be speaking. French girls often do the like; from them she had caught the custom. `Chose,' however, I found, in this instance, stood for Villette - the great capital of the great kingdom of Labassecour." (Ch. 6) Villette in fact is a version of Brussels.

I should add that the only place name on Terra rather than the antiterras of fictionš that is called “Villette” is in Vaud Canton, between Montreux, where Nabokov lived while writing ADA, and Lausanne, where he would visit his tailor every year to have new shorts made for him for butterfly hunting. Passing Villette so often for this and other reasons COULD have piqued Nabokov’s curiosity to read the novel. But it’s improbable, and even if he did, offers no link with Cambridge.