[cycjec]

COSTCO delenda est. (deleo, delere, delevi, deletum)
That assumes “COSTCO” is feminine in gender.
COSTCO delendus est for masculine.
I *could* explain how ppl put “a”s where “e”s belong
but sometimes I’d be wrong and it would just add to
general confusion.

[muawiyah]

"Cartago" was masculine, but the modifier "Delando" is NEUTER ~ neither male nor female. I think the meaning is "Dead is Dead" (if it's just kind of standing alone out there with nothing to modify).

The period of time we are talking about (Carthaginian wars) had the Romans thinking of place names as not having gender, and only later did they demand intense correspondence of the FORM of the noun and its MODIFIERS.

Best not to think back from modern Romantic languages to ancient Latin. A better referent would be to what the Celts and Germans were up to, then, once the Romans had totally conquered and absorbed the Greek empire, you would want to see what the Greeks were doing linguistically. No doubt when the Romans "went city" they spruced up their grammar! Back when they were still a melange of unassimilated country boys, they could have said just anything.