Definition of pall:
fine cloth, especially purple cloth used for robes; a cloth
used for various purposes on the altar
in a church
"1942: Thirty years or so later, a woman was put to death for stealing the purple pall from his sarcophagus, a strange, crazy crime -- Rebecca West, Black Lamb and Grey Falcon (Canongate 2006, p. 150)"
to make vapid
; to make lifeless or spiritless; to dull; to weaken