I looked up the dictionary definition of pretentious, and so it doesn't really apply, but the hERG channel is a critical ion channel and various drugs block this and cause Really Bad Things. hERG stands for "the human Ether-a-go-go-Related Gene" - a pretty bloody stupid name but whimsey is not restricted to particle physics.
Canonical ensemble, along with microcanonical and grand canonical ensembles are all over statistical mechanics. And I suspect there's not one bit of whimsey in their naming. There was not any humour in my stat mech course aside from me trying to make sense of it.
—the Grand canonical ensemble
Also, "the free will theorem" and "the god particle".