from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An opaque fabric mounted to cover or expose a window.
from the GNU version of the Collaborative International Dictionary of English
- n. a shade or blind for a window; usually, one that is hung on a roller.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. an opaque window blind that can cover or uncover a window
Sorry, no etymologies found.
Now as to the pattern into which this information may fit: As I mentioned, Mrs Rogers is a talkative woman, easily steered into one topic and another, with certain very definite exceptions, when a thick window shade is pulled down behind her eyes and she discovers that it is time to make a pot of tea or check on her aged mother.