When bitcoin forks, how do they decide which fork gets the original name?

Question

Bitcoin has had a number of forks over the years. The biggest one was Bitcoin and Bitcoin Cash.

Bitcoin seems to have won out in this fork, and is much more popular than Bitcoin Cash.

However, how was this naming scheme agreed? Why did Bitcoin end up still allowed to be called Bitcoin, whereas Bitcoin Cash needed a new name?

Arguably the fork that had the original name had a much bigger advantage in "winning out" over the one with the new name.

For example, Ethereum also had a fork and it was the original Ethereum that needed a new name (Ethereum Classic) and in that case, the new Ethereum (the fork we know now) was the one that won out.

Answer 1

One might think that the network maintaining the same consensus rules would be considered the original, and the project introducing a consensus rule change and thus creating a new network would be considered the derivative, but you've already pointed out an exception to that rule with the ETH DAO fork. Various arguments can be made why one or the other network should have been named ETH in that case. Similarly, with Bitcoin and Bitcoin Cash, proponents of Bitcoin Cash had attempted to claim the name Bitcoin for their own network.

Looking at a few fork events, the rule seems to rather be that the dominant fork gets to keep the name. However, it might not be obvious prior to a split which project will end up being recognized by the majority. In the advent of the Bitcoin Cash fork and the Segwit2x fork attempt, futures markets gave some indication how the public valued each proposal. Yet, in the end, it's an emergent social phenomenon. Whatever "everyone" ends up calling Bitcoin is Bitcoin. Often this conflict is resolved when one of the two networks rebrands.