Things That Go Bump In The Night Meaning

(idiomatic) Frightening imagined creatures; ghosts or other supernatural beings.

Example: 1940, "Life on the Newsfronts of the World," Life Magazine, 7 Oct., p. 32:
  Hellish new noises from new and secret British anti-aircraft devices vibrated last week through the din of London bombings. . . . [T]hey must have reminded Londoners of the old litany:
  From ghoulies and ghosties,
  Long leggety beasties
  And things that go bump in the night
  Good Lord, deliver us.
1961, May Mackintosh, "If I Were a Witch," The Glasgow Herald, 27 Oct., p. 7:
  But most of all I recall the haunting magic of the lanterns and the whispered tales of ghosties, goblins, and things that go bump in the night with which we tried to frighten each other.