You don't have to be old to be ignorant. "Mainnet," and "Chain," have non-arbitrary, universal meaning in the distributed ledger space. 'Beacon' is not arbitrar

You don't have to be old to be ignorant. "Mainnet," and "Chain," have non-arbitrary, universal meaning in the distributed ledger space. 'Beacon' is not arbitrary either as it fits the function it names. I'm not going to sit here and defend Ethereum - but to answer you question: most of that verbage has meaning independent of Ethereum's PR.