Nice one, didn't think of that ! I suggested the one-letter town Y (population : 89), which is obviously much less well-known, but is also much smaller.
Edit : just realised, the airport city Roissy-en-France at under 3k inhabitants is a huge contender too that wasn't mentioned
In France it might be Y (population : 89), famous for having a one-letter name. Far from "anyone can still instantly recognise the name" but still probably much more well-known than any other town this size.
Otherwise idk, feels like the only french city everyone would instantly recognise the name of is Paris tbh.
Except no one would be able to read your comment before posting because, again, no consequence. So that's pointless.
No one yet has mentioned a common yet pretty bad first name : Dick.