midnight drop
n.— «According to the Dow Jones report, the US Treasury is trying to push the regulations through after months of difficult drafting in the hope of finalising the issue before the Bush administration leaves office at the end of the year. The Treasury Department forwarded the final regulations to the Office of Management and Budget on October 21, a necessary step towards implementation. The report describes the move as standard practice for outgoing administrations to finalise controversial regulations before leaving office, a practice known as a midnight drop.» —“U.S. Officials Race To Finalise UIGEA Regs” Online-Casinos.com Nov. 7, 2008. (source: Double-Tongued Dictionary)
This was in use in British press circles some years ago , before e-mail , electronic compositing and newspaper websites with rolling news came along .
If a “source” had a piece of “confidential” news he wanted “leaked” into the public domain , it would be arranged that the incriminating document would be dropped at the chosen newspaper’s main office at [supposedly] midnight – time enough for the splash to make the later editions , but not early enough that the rival newspapers could pick up on it and run it .