The OED finds pompaticus as “showy, splendid” in Tertullian from as an adjective dating from Late Latin deriving from pompare, “to do a thing with pomp.” Pompatus per se is some weird-ass declension that I can’t hope to figure out from the abbreviations.
If you’d like to insert in an offhand bon mot the archaic English word “pompatic,” go for it. OED dates it from 1535, and the latest at 1903, probably used by some pedant (not that Cecil is; he’s just scary smart).
Leo