fog

Etymology 1

Origin uncertain; but probably of North Germanic origin. Probably either a back-formation from foggy (“covered with tall grass; thick, marshy”), from the earlier-attested fog (“tall grass”) (see below), or from or related to Danish fog (“spray, shower, drift, storm”), related to Icelandic fok (“spray, any light thing tossed by the wind, snowdrift”), Icelandic fjúka (“to blow, drive”), from Proto-Germanic *feukaną (“to whisk, blow”), from Proto-Indo-European *pug- (“billow, bulge, drift”), from *pew-, *pow- (“to blow, drift, billow”), in which case related to German fauchen (“to hiss, spit, spray”).

noun

1. (uncountable) A thick cloud that forms near the ground; the obscurity of such a cloud.
   a bank of fog
   Wallis and Curtiz eventually agreed to shoot Howard Koch’s preferred ending, with distraught Ilse, still in love with Rick, going off with Laszlo to America, and Rick and Louis going off together into the fog. (In Morocco? Fog? Never mind.) March 19, 2012, David Denby, “Everybody Comes to Rick’s: “Casablanca” on the Big Screen”, in The New Yorker
2. (uncountable) A mist or film clouding a surface.
3. (figurative) A state of mind characterized by lethargy and confusion.
   He did so many drugs, he was still in a fog three months after going through detox.
   I was on my way to the door, but all at once, through the fog in my head, I began to sight one reef that I hadn't paid any attention to afore. 1913, Joseph C. Lincoln, chapter 4, in Mr. Pratt's Patients
4. (photography) A silver deposit or other blur on a negative or developed photographic image.
5. (computer graphics) Distance fog.

verb

1. (intransitive) To become covered with or as if with fog.
2. (intransitive) To become obscured in condensation or water.
   The mirror fogged every time he showered.
3. (intransitive, photography) To become dim or obscure.
4. (transitive, photography) To make dim or obscure.
5. (transitive, photography) To spoil (film) via exposure to light other than in the normal process of taking a photograph.
6. (transitive) To cover with or as if with fog.
   Fogging for adult mosquito control began on June 4th in residential areas. Until September 25th, the Metro area was fogged eleven times, using nine truck-mounted foggers, eight hand swing foggers, and two boats. 1968, Eighth Annual Report, Metropolitan Corporation of Greater Winnipeg, page 7
7. (transitive) To disperse insecticide into (a forest canopy) so as to collect organisms.
8. (transitive) To obscure in condensation or water.
   Unfortunately, the pendulum has swung way too far to the other end where the saying in the industry is is that if you could fog a mirror, you could get a loan. 2008, United States Congress, House Committee on Financial Services. Subcommittee on Housing and Community Opportunity - Foreclosure, Foreclosure Prevention and Intervention: The Importance of Loss Mitigation, page 46
9. (transitive) To make confusing or obscure.
10. To practice in a small or mean way; to pettifog.

Etymology 2

From Middle English fogge (“tall grass”), probably from Norwegian fogg (“tall, worthless grass”); compare Scots fog (“moss; lichen”).

noun

1. A new growth of grass appearing on a field that has been mowed or grazed.
   The inclosures of fog, or aftergrass, reserved for spring-feed, are now supposed to be shut up, also the burnet, which is never to be fed in autumn ... 1800, John Lawrenece, The New Farmer's Calendar; Or, Monthly Remembrancer, for All Kinds of Country Business: Comprehending All the Material Improvements in the New Husbandry ... By a Farmer and Breeder [i.e. J. Lawrence]., page 114
2. (UK, dialect) Tall and decaying grass left standing after the cutting or grazing season.
   […] and they generally leave a great deal of Fog to rot on the Ground, which, with the Help of his well turned Dung-hill, dress his Ground […] 1744, William Agric Ellis, The Modern Husbandman, page 104
3. (Scotland) Moss.

verb

1. (transitive) To pasture cattle on the fog (of), or aftergrass, of; to eat off the fog from (a field).
2. (intransitive) To become covered with the kind of grass called fog.