Of American-English origin, the phrase butterflies in one’s stomach denotes an uneasy sensation felt, especially in the stomach, as a result of nervousness or apprehension.
This phrase is based on the notion that the fluttering of butterflies may produce a similar sensation.
An early use of the metaphor, with the singular butterfly, occurs in the following passage from The House of Prayer (1908), by the U.S. author Florence Converse (1871-1967)—as quoted in the Oxford English Dictionary (3rd edition, 2018):
The three o’clock train going down the valley […] gave him a sad feeling, as if he had a butterfly in his stomach.
An early use of the phrase, apparently referring to an hallucination experienced by an alcoholic, occurs in China Seas (1935), a U.S. adventure film directed by Tay Garnett, starring Clark Gable, Jean Harlow and Wallace Beery—according to the review of this film, published in The Philadelphia Inquirer (Philadelphia, Pennsylvania) of Saturday 17th August 1935:
There is Robert Benchley *, as a happy drunk who whispers solemnly, “Don’t look now, but I think I’ve got butterflies in my stomach.”
* Robert Benchley (1889-1945) was a U.S. humorist and actor.
The earliest occurrence that I have found of the phrase—in the sense of an uneasy sensation felt as a result of nervousness—is from the account of a golf match between Nick Welch and Henry Duyck, published in the Moline Daily Dispatch (Moline, Illinois) of Tuesday 31st August 1937:
The “giant killer’s” next shot was the “pay-off” because it was so deadly that it apparently caused Nick to suffer a sudden attack of “butterflys-in-the-stomach.”
An early variant of the phrase occurs in Peggy Harding’s column Off The Record: Society Chatter, about rush week at Austin College, published in The Austin Statesman (Austin, Texas) of Friday 24th September 1937:
With the rushees frightened silly, and I mean silly, that they will not make a good impression, they have let fall some prize cracks that bear evidence of sleepless nights thinking up witty things to say. With a great display of vivacity one rushee popped “I’m so nervous I feel that I have pink butterflies all over my stomach.”
The phrase occurs in an article about the U.S. actor Alan Curtis (Harry Ueberroth or Harold Neberroth – 1909-1953), published in the St. Louis Globe-Democrat (St. Louis, Missouri) of Thursday 20th January 1938:
Hollywood, Cal.—Alan Curtis left New York for Hollywood with 52 suits of clothes, train fare home and a prayer. That was 16 months ago. […]
“And I’m still praying,” Curtis said, confidentially.
He even talks with his fingers crossed.
Curtis has been that way ever since the day he walked into Director Frank Borzage’s office, an unknown young actor, with is hat in his hand and butterflies in his stomach. He emerged with one of the year’s fattest parts in “Mannequin” and the jitters.
The following is from the column The Village Smithy, by Chester L. Smith, Sports Editors, published in The Pittsburgh Press (Pittsburgh, Pennsylvania) of Tuesday 30th August 1938:
An “Old Time Fan” has no great complaint with the Pirates, adding a word of praise for the way in which the customers and newspapers have supported them this year, but he does think of a way out of their present dilemma. He suggests that scouts be dispatched immediately to bring in a pinch-hitter to displace either Jensen or Dickshot and a pitcher to be used instead of either Joe Bowman or Bill Swift. The rest of the boys, he believes, are suffering from butterflies in the stomach, and would be bolstered no end by such a move.
An inebriated man, referred to as Mr. X, reportedly described as butterflies his stomach a physical sensation that he experienced, in the account of an experiment undertaken to find out whether a fire-department inhalator could cure a hangover—account by Theon Wright, of United Press, published in several newspapers in October 1938, for example in The Courier-Journal (Louisville, Kentucky) of Saturday the 22nd:
Mr. X was inspected and it was noted that his eyes had “cleared up” and he said some of the butterflies in his stomach had gone to sleep.
An interesting extended metaphor describing a physical sensation felt in the stomach occurs in the “account of life aboard a transatlantic liner, as it appears to one making her first crossing”, by “Miss Josephine Howell of Abilene, who sailed to England Sept. 20 to marry an officer in the British army’s intelligence service”—published in The Abilene Reporter-News (Abilene, Texas) of Sunday 6th November 1938:
Try as I may, I couldn’t stand up straight in accordance with the walls around me. They moved with such slowness, that it made me dizzy to try to follow them, so I decided I must get on my clothes and do a few turns around the deck (that is what I had read people do when on a ship) so I closed my eyes, and with much groping, grunting, and yes—some swearing, I finally got into a house dress, but guess what?? I at once discovered I had butterflies in my stomach. They would sway with the motion of the boat, and they just wouldn’t get away from the walls of my stomach at all. I tried coaxing and made all kinds of promises, that I knew I couldn’t keep, but no, they stayed.
[…] I finally got up enough nerve (and it took a lot) to swallow the orange juice, which took only two gulps, and noticed about that time a cup of steaming coffee being set down to my right. It smelled so good and I laughed silently to myself thinking of the fate of my good enemies, the butterflies. But, I had smiled entirely too soon, for the moment I opened my mouth over the side of the cup, I knew a mistake had been made. It was that horrible old siruppy [sic] Louisiana coffee, which I detest. I could hear the butterflies laughing with glee, so I said, “All right, if that is the way you feel about it, you win, but just for the moment.”
After the first day out and I got rid of the butterflies, I have felt grand and eaten like a horse.
A different metaphor occurs in the account of a downhill race held on Bald Mountain, in Idaho, published in The Oregonian (Portland, Oregon) of Sunday 19th January 1941:
The Oregon kids had “butterflies flopping around like eagles” when they made their first runs. But they soon got over their nervousness and found that it was easier to ski on these slopes than on the flatter ones they were used to.
The phrase butterflies in one’s stomach soon came to be shortened to butterflies—as in the following from A Paratrooper’s First Jump, as described in a letter to his mother and printed in the New York Times, published in The Ottawa Evening Journal (Ottawa, Ontario) of Wednesday 28th October 1942:
I felt my heart drop down to my shoes, but I closed in on the man ahead of me […].
When I met some of my friends we discussed the whole thing, and it seems that everybody had as many butterflies as I did, and the same heart-sinking feeling.