nightgloom

Either from night +‎ gloom or a learned borrowing from Old English nihtglōm,

nightgloom (uncountable)

1. (rare, literary) Darkness of the night; night gloom.
   • 1850, H. L. H., “Confessions from the Christian Camp”, in The Reasoner, volume VII, London, page 1:

     […] how we longed to be the hero, how the burning ardour for adventure arose within us, and we sought wistfully with eager eyes to find somewhere in the world around the footprints of temerity, listening breathlessly even in the nightgloom for the sound of their creation, doubting not ‘the deeds that we would do or die.’

   • 1875 May 1, Goethe [i.e., Johann Wolfgang von Goethe], “The First Walpurgis-Night”, in W. Bartholomew, transl., Dwight's Journal of Music, volume XXXV, number 2, Boston, page 2:

     No. 6.–Chorus of Guards and People.
     
     Come with torches brightly flashing,
     Rush along with billets clashing,
     Through the nightgloom, lead and follow,
     In and out each rocky hollow,
     Owls and ravens,
     Howl with us, and scare the cravens!

   • 1975, Will Bradford, “A Quickening Pace to Events” (chapter 5), in The Butte Country, Great Britain: Robert Hale & Company, page 46:

     Perry turned and contemplatively watched the lawman’s thick torso moving up through the increasing nightgloom, ‘What the hell do you suppose it is that he knows about us, for a fact?’

   • 2011, Ed Greenwood, “Let It Begin” (chapter 7), in Bury Elminster Deep, Wizards of the Coast, page 62:

     Because I've been hacking at wolves in forests for far more than a thousand years longer than ye have—and I know I can't, when nightgloom gets this deep.’