1897, "scenery and furnishings," from French décor (18c.), back-formation from décorer "to decorate" (14c.), from Latin decorare "to decorate, adorn, embellish, beautify," from decus (genitive decoris) "an ornament," from PIE root *dek- "to take, accept" (on the notion of "to add grace"). The modern word thus duplicates Latin decor "beauty, elegance, charm, grace, ornament."
Originally in English in reference to theater stages; home-decor is by 1900 in reference to copies of old masters paintings used as home decoration; general use for "decorations and furnishings of a room, building, etc." is by 1926.