As for libertarian/liberal - as Tom says libertarianism is a form of liberalism, I’d go so far to say that many US liberals are not liberal, they’re collectivists - which goes directly against liberalism.

Note its also possible to be a Liberal but not be a liberal - Chamberlain was arguably in this category, I’m sure there are others people can think of…

“Libertarianism” is an American attempt to find a name for liberalism. The USA was founded on liberal principles to such an extent that they were taken as read, so that the term was not used in ideological debate. It was later coined by social reformers who were in fact more interested in equality than liberty, and hence the old guard (which in America was liberal rather than what we would consider conservative) were seen as libertarian in counterweight to the egalitarian self-styled “liberals”.

And the People’s Popular Front of Judea (splitters!).….

Another way to look at it is the debate between what one might call the “Gladstone Liberals” and the “Lloyd George Liberals”.

In the end, however, we’re quibbling. If you believe that society should allow the individual the maximum amount of freedom possible such that it does not limit the freedom of others, then Milton Friedman is an inspiration.