Thank you, kind sibling. This rift is the most frustrating diplomatic choice I've ever seen America make. I hope we can make it right and grow closer someday.
Do is the root of a key in movable Do solfeggio. In the most natural key, C, Do would be C. Basically, solfeggio is relative, not absolute. Most instrumental pedagogy use absolute pitches in North America. Vocal pedagogy has more use of relative pitches. This makes sense, as many instruments have absolute means of playing most notes. The voice does not.
Circa 1990 didn't get smartphones as teens. The iPhone launched on only AT&T in the US in 2007. We were all locked into 2 year contracts back then with LG Envys and Motorola Razrs.
Endonym vs exonym is a universal truth of contact between speakers of different languages. It is in no way unique to English.