A fantod is a very bad mood or a feeling of extreme upset or anxiety. The word usually appears in the plural form, fantods, as in “I had the fantods all morning.”
Fantod’s exact derivation is unknown, though it seems to have originated in the early 19th century. The OED calls it “an unmeaning formation suggested by fantastic,”1 Merriam-Webster says it’s possibly a blend of fantastic and fatigue,2 and several sources, including the OED, say it’s probably related to fantigue, a 19th-century British dialectical word that is almost exactly synonymous with fantod.3
This sentence, from the 1839 book The Adventures of Harry Franco by American writer Charles Briggs, has been said to contain the first instance of fantods in English4:
You have got strong symptoms of the fantods; your skin is so tight you can’t shut your eyes without opening your mouth.
But Google Books uncovers two examples from 1835. The first is from an essay (with no attributed author that we can find) in The Metropolitan, a monthly magazine published in London (interesting because the word is now mainly an Americanism) from 1831 to 1850:
There is an indescribable complaint, which will never allow a moment’s repose to mind or body; which nothing will satisfy—which allows of no beginning, and no ending—which wheels round the mind like a squirrel in its cage, ever moving, but still making no progress. It is called the Fantods.
[B]ut your excellency knows I’ve something better to do, than tend to all their ‘lectioneering fantods.”
The first example seems to suggest that Fantods might have been a new word in 1835, but its use in the second example suggests it might have been an established dialectal term before then.
Instances of fantods are scarce in published books and news sources up to around 1880, after which the word becomes rather common. Its growth after 1880 and its continued (albeit rare) use today might be partially due to Mark Twain’s use of the word (which he spelled fan-tods) in several of his famous works.
These were all nice pictures, I reckon, but I didn’t somehow seem to take to them, because if ever I was down a little, they always give me the fan-tods. [The Adventures of Huckleberry Finn, by Mark Twain (1884)]
The editor of the Spartanburg Journal appears to be afflicted with a very bad case of fantods, and in scanning the political horizon cannot see the faintest glimmer of hope … [Victoria Advocate (1903)]
Sometimes I’m so mad about it I want to fight someone. It gives me the fantods. [“I Want to Know Why,” by Sherwood Anderson (1921)]
In full credit to Mr. Eisenhower, there has always been an exceptional candidness about his exposure to the public of his migraines and various fantods. [Sarasota Herald-Tribune (1957)]
[I]t was always easy, in open and lonely places, to be visited by Panic wildness fear, but these are the urban fantods here, that come to get you when you are lost or isolate inside the way time is passing … [Gravity’s Rainbow, by Thomas Pynchon (1995)]
And Sam’s panicked stasis, both social and professional, corresponds to a recognizable epidemic of the howling fantods in our nation’s graduate schools. [New York Times (2012)]