darken

Etymology

From Middle English derkenen, dirkenen, from Old English *deorcnian, *diercnian (“to darken”), from Proto-West Germanic *dirkinōn (“to darken”), equivalent to dark + -en. Cognate with Scots derken, durken (“to darken”), Old High German tarchanjan, terchinen (“to darken”), Middle High German terken, derken (“to darken”).

verb

1. (transitive) To make dark or darker by reducing light.
2. (intransitive) To become dark or darker (having less light).
   […] the owl and the bat flew round the darkening trees: 1783, William Blake, “The Couch of Death”, in Richard Herne Shepherd, editor, Poetical Sketches, London: Basil Montagu Pickering, published 1868, page 84
   […] leaning at her window she watched the end of that eventful day darken over the ranges. 1930, Zane Grey, “Chapter Twelve”, in The Shepherd of Guadeloupe
3. (impersonal) To get dark (referring to the sky, either in the evening or as a result of cloud).
   Then they passed out from the Forum, forced their way through the crowded streets, and soon were through the Porta Ratumena, outside the walls, and struck out across the Campus Martius, upon the Via Flaminia. It was rapidly darkening. 1901, William Stearns Davis, “Chapter 4”, in A Friend of Cæsar, New York: Macmillan, page 57
   From babyhood until fourteen, to play in a garden in the evening when it is darkening is a legend. 1945, Gertrude Stein, Wars I Have Seen, London: B.T. Batsford, page 13
   It had been fine all morning, but it was darkening now, the weather was going to get worse. 1996, Colm Tóibín, “Portrait of the Artist as a Spring Lamb”, in The Kilfenora Teaboy: A Study of Paul Durcan, Dublin: New Island Books, page 7
   He looked up. It was darkening here as well. Sky getting red, the edge of the quarry dark and jagged against it. 2005, David Almond, chapter 10, in Clay, London: Hodder Literature, page 44
4. (transitive) To make dark or darker in colour.
   She puts on lipstick and darkens her eyebrows, which are now very scanty […] 2009, Alice Munro, “Free Radicals”, in Too Much Happiness, Toronto: McClelland & Stewart, page 118
5. (intransitive) To become dark or darker in colour.
   The lovely hair had lost its rose-gold glimmer, and had darkened to rose-brown […] 1979, Mary Stewart, The Last Enchantment, New York: Fawcett Crest, Book 4, Chapter 4, p. 405
6. (transitive) To render gloomy, darker in mood.
   It was a pleasure seeing you again. I’m only sorry I had to darken the pleasure with my private problems. 1969, Chaim Potok, chapter 4, in The Promise, New York: Fawcett Crest, published 1872, page 89
7. (intransitive) To become gloomy, darker in mood.
   1797, Ann Radcliffe, The Italian, London: T. Cadell Jun[ior] and W. Davies, Volume 2, Chapter 9, p. 303, His countenance darkened while he spoke […]
8. (transitive) To blind, impair the eyesight.
   1773, Samuel Johnson, letter to James Boswell dated 5 July, 1773, in James Boswell, The Life of Samuel Johnson, Volume I, London: Charles Dilly, p. 424, When your letter came to me, I was so darkened by an inflammation in my eye, that I could not for some time read it.
9. (intransitive) To be blinded, lose one’s eyesight.
10. (transitive) To cloud, obscure, or perplex; to render less clear or intelligible.
    His [Edmund Spenser’s] stile was in his own time allowed to be vicious, so darkened with old words and peculiarities of phrase, and so remote from common use, that Johnson boldly pronounces him to have written no language. May 14 1751, Samuel Johnson, The Rambler, volume 4, number 121, London: J. Payne & J. Bouquet, page 193
11. (transitive) To make foul; to sully; to tarnish.