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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/
They were numbered in the order that they were "discovered" (or theorized, in the case of population III). Similar to how exoplanets around a particular star are designated "a", "b", "c", etc. in order of discovery, so they usually end up not in any particular order. Sometimes letters end up skipped when a letter is assigned and then it's discovered to be a false positive.
So there's logic to it, just not the logic one might prefer.