Title text:
The family lore was that we've had it ever since it was ejected from a star-forming gas cloud, but it seems more likely that my great-grandparents probably just bought it while on vacation in the galactic thin disk.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3281/
It would be tricky to change a designation after the fact. If you retroactively designated all "Population I" stars as "Population II", then from then on every time you read any scientific literature you'd have to figure out when it was written so you'd know what they meant by it, and for stuff written around the time of the transition you'd have to ask the authors what they meant directly, and--
Language is supposed to make communication easier. Ambiguity in terms inevitably does the opposite.