Mission creep is the gradual expansion of a mission beyond its original scope. The phrase first appeared in print in 1993, in coverage of the UN mission in Somalia. Jim Hoagland of The Washington Post used it that April, and titled a column in July “Beware ‘mission creep’ In Somalia.”
The New York Times used it after the firefight in Mogadishu on October 4, 1993, in which eighteen American military personnel were killed.