Trip To The Woodshed Meaning

(chiefly US, idiomatic) An occasion on which a reprimand or punishment is administered.

Example: 1948, "Sweet Reasonableness," Time, 13 Dec.,
  More than a few of the 3,000 members of the National Association of Manufacturers, gathered for their annual convention in Manhattan's Waldorf-Astoria Hotel last week, felt like small boys worrying about a trip to the woodshed. None knew how vindictive or friendly toward business the Truman Administration would be.