Where does “core city” come from?

core city (English) comes from English Core, from English -core, from English hardcore, from English hard, from Old French hardi, from Old French hardir, from Frankish hardijan, from Proto-Germanic hardijaną — to travel, tour.

Ancestry of “core city”, step by step

core city traces back through two separate lines of ancestry.

via English Core

StepLanguageWordMeaning
1EnglishCoreThe birth name of Persephone/Proserpina, the queen of the Underworld/Hades, and goddess of the seasons and of vegetation. She is the daughter of Zeus and Demeter, and the wife of Hades
2English-coreApplied to various genres of music and...
3EnglishhardcoreHaving an extreme dedication to a certain...
4EnglishhardHaving a severe property; presenting difficulty;...
5Old Frenchhardihardy; tough; durable
6Old Frenchhardirto harden
7Frankishhardijanto harden, to make hard
8Proto-Germanichardijanąto make hard, strong; to harden
9Proto-Germanicharduzhard; brave
10Proto-Indo-Europeankert-times; to weave, twist together; time
11Proto-Turkic*keŕ-to travel, tour

via English city

StepLanguageWordMeaning
1EnglishcityA large settlement, bigger than a town; sometimes...
2Middle Englishcitecity
3Old FrenchcitetAlternative form of cité
4Latincīvitās
5Proto-Italickeiwissociety; citizen
6Proto-Indo-Europeanḱey-to be lying down; to settle
Every word from Proto-Turkic *keŕ-Every word from Proto-Indo-European kert-Every word from Proto-Germanic harduz