"surgical operation making a permanent opening in the body," 1957, abstracted from colostomy, etc.; ultimately from Modern Latin stoma "opening, orifice," from Greek stoma "mouth" (see stoma).

"reduce in size or scale," 1945, American English, from down (adv.) + scale (v.). In business, especially, "to reduce the size of an operation." Related: Downscaled; downscaling. From 1966 as an adjective.

mid-14c., "an act of elevating," verbal noun from raise (v.). Specifically in American English, "the erecting of a building," by 1650s.

RAISING. In New England and the Northern States, the operation or work of setting up the frame of a building. [Webster, 1830]

1888, from combining form of colon (n.2) + Modern Latin -stoma "opening, orifice," from Greek stoma "opening, mouth" (see stoma). Colotomy "operation of making an incision in the colon" is attested from 1860, from Greek tome "a cutting."

1918, "date set for the beginning of a military operation," with D as an abbreviation of day; compare H-hour, also from the same military order of Sept. 7, 1918:

The First Army will attack at H-Hour on D-Day with the object of forcing the evacuation of the St. Mihiel salient. [Field Order No. 8, First Army, A.E.F.]

"They designate the day and hour of the operation when the day and hour have not yet been determined, or where secrecy is essential" [U.S. Army Center of Military History Web site]. Now almost exclusively of June 6, 1944.