Did you know that tripping the light fantastic means to dance nimbly or lightly? As far as idioms go, this is what is called a non-compositional constructionally idiosyncratic form, which means that the word associations in the phrase make more or less no literal sense - someone just sort of made it up. When I was a kid, I used to rack my brain (idiom with a compositional but experientially unrealistic literal meaning) to conceptualize how turns of phrase could potentially start with one person's expression, and then spread. Or crazier, if people in different places could come up with the same expression, simultaneously, based on some kind of common or collective influences. Needless to say, this was before the internet.