Although similar to the gloaming, grimmelings is a slightly different natural phenomenon at both ends of the rotating sun’s traverse across the sky.
Grimmelings – The first or last gleams of the day (Scots, esp. Orkney).
From the Norwegian “grimla”, to glimmer before the eyes, to twinkle or blink. Also “grimlins”.
Or “the harlot’s hour”: “Just in the close and shutting up of day, When the last gleams were hurrying swift away; The harlots hour their subtle trains to lay” Robert Gould’s 1689 Paraphrase of Proverbs 7 (KJV has “in the twilight, in the evening, in the black and dark night”)