French

Noun

coup de main m ‎(plural coups de main)

1. a helping hand (assistance)
2. a sudden development or action to surprise an enemy
   • 1857, Anthony Trollope, Barchester Towers, Volume the Second, page 78 (ISBN 1857150570)

     That which of all things he most dreaded was that he should be out-generalled by Mr. Slope; and just at present it appeared probable that Mr. Slope would turn his flank, steal a march on him, cut off his provisions, carry his strong town by a coup de main, and at last beat him thoroughly in a regular pitched battle.