1
general::
Present or make known unexpectedly, as in They sprung the news of their engagement on the family last night. This idiom uses spring in the sense of "make a sudden move." Mark Twain used it in Tom Sawyer (1876): "Old Mr. Jones is going to try to spring something on the people here tonight." Make neat and trim, as in She spruced up the chairs with new cushions. This idiom originated in the late 1500s as simply spruce but had acquired up by 1676. In addition to the idiom beginning with SPUR, Also see ON THE SPUR OF THE MOMENT; WIN ONE'S SPURS.
American Heritage Idioms