The dictionary says "Firlefanz {m}
frippery
folderol
doohickeys [coll.] {pl}
foofaraw
furbelows
gew gaws

No mention of being a Luxembourg regionalism.

I'm not sure about the meaning of the poem, but maybe the parson, upon inspiration from his terrific hat, resorts successfully to "furbelows" to impress the other clergymen of the synod, who don't know their Latin either? The ring - an imagined saint's halo?

Other suggestions?