"Mama, what's a reredos?"
"A reredos, dearest creature, is an architectural term meaning, among other things, the screen or decorated portion of the wall behind the altar in a church."
"Oh. So at St. Peter's, the painting covers the reredos -- is the reredos."
"Cool. May I please have a cookie?"
"Yes, and do put your brother's iguana down. You'll get him sticky."