1988 is what I remember because at the time watching the way H.W. spat the term it struck me as quite odd and I thought, "is that going to work"? Then I remembered the observation of H.L. Mencken and realized that it probably would
That the left, or more accurately the "Democrats", called themselves liberals is understandable given their legacy of association with the commoner classes; after all when they oppose e.g. gay marriage laws in favor of letting gay couples be, they are practicing Liberalism. OTOH when they start legislating affirmative action or banning big sugar drinks, that's Leftism. Passive versus active to oversimplify it.
Republicans practice Liberalism too when they stand for certain (but not all) deregulation, e.g. of small businesses. And they should be proud to tout it when they do.
Of course,
some amount of regulation is necessary in any society, unless we want anarchy (which is what I associate the term "libertarian" with and why I don't use it). You can't have a system of roads, and yet oppose the idea of traffic lights. If your business is, say, food production, there must be some authority in place to ensure you're not disseminating e coli or something. That's where we need the balance of left and right on top of a Liberalist framework. A minimal boundary line set by the people, for the people. But not no boundary lines at all.
But to dichotomize right and left into a vast swamp of heroes and monsters so that we can eliminate the monsters, is a competitive rather than cooperative philosophy, and benefits no one except those who see politics not as a vehicle not for sociopolitical philosophy but for a meaningless football game. That's why I oppose these linguistic distortions.
(rant off/offtopic)