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The jocular American-English phrase to get one’s panties in a bunch (also in a wad, in a knot, etc.) means: to become unduly agitated or angry.
In this phrase, the plural noun panties refers to short underpants worn by women or girls.
The synonymous British-English and Irish-English phrase is to get one’s knickers in a twist (the plural noun knickers refers to short underpants worn by women or girls).
—Note: The variant to get one’s panties in a twist is rare in British English and Irish English.
These are, in chronological order, some of the earliest occurrences that I have found of the American-English phrase to get one’s panties in a bunch (also in a wad, in a knot, etc.):
1-: From the column On the Screen, by Jim Skinner, published in The Brandon Sun (Brandon, Manitoba, Canada) of Friday 21st March 1975 [page 11, column 3]:
What about putting a levy on all non-Canadian films and using the proceeds to finance the domestic industry? First off, admission prices would go up to pay the “extra.” Then there is the question of who would get the money. Cinepix of Montreal is the most profitable of all Canadian production companies, but it specialises in soft-core pornography. Do we really want to pay more to see “Towering Inferno” or “Godfather II” so that Jacques Lefevre or whoever can make a remarke [sic] of “Don’t Get Your Panties In A Twist?” *
* I have not found any mention of a film called Don’t Get Your Panties in a Twist. But the allusion may be to Don’t Get Your Knickers in a Twist, the title of an X-rated film mentioned, for example, in the cinema programmes published in The Observer (London, England) of Sunday 11th February 1973.
2-: From Reactions vary about success of the Falcons, by C. B. Hackworth, published in The Times (Gainesville, Georgia, USA) of Sunday 14th December 1980 [Section B: Sports, page 1, column 1]:
In case you missed last Sunday’s paper, Phil [Jackson] published some not-very-complimentary observations about the Atlanta Falcons, which is almost as suicidal as standing in the middle of a redneck diner and screaming, “What’s this awful stuff?” when the waitress brings you grits.
[…]
[…] I’m afraid too often we read and react only to isolated passages without taking into account the argument in its entirety. This was done by most of the disgruntled Falcon fans, including some I’d have thought would know better, who got their panties in a wad over this Jackson paragraph.
3-: From an advertisement for the shopping centre Parks Belk, published in The Jackson Sun (Jackson, Tennessee, USA) of Friday 9th October 1981 [page 6-A, column 4]:
LOUSY LINGERIE
[…]
Ladies’ Bras and Girdles: Who needs cups and bags, we don’t… Do You? (Only for women smuggling watermelons across the border). 49% off
Ladies’ Panties: If you want to get your panties in a wad, these are a creeping good buy. orig. 5.00, 1.74
4-: From Psychiatrists don’t like it, by C. B. Hackworth, published in The Times (Gainesville, Georgia, USA) of Sunday 11th April 1982 [page 2-C, column 3]—C. B. Hackworth has first quoted a letter in which the Georgia Psychiatric Association complained about the “unfair and repugnant portrayal of psychiatrists and the practice of psychiatry” in the television series Dynasty:
The Public Relations Society of America, of which I was once a member, recently got its panties in a similar wad over the Susan Flannery character in Dallas, who used sex to land herself a job as public relations director of Ewing Oil.
5-: From the following advertisement, published in The Daily Tar Heel (Chapel Hill, North Carolina, USA) of Monday 25th April 1983 [Classified ads: Personals, page 2, column 6]:
TO ALL 4TH WEST FAUNKS: Squirtski, ‘B’ Hunter, Guilty, Gondola, Clopwad, Prima, Playboy, Party Woman, Roweena, Queen Faunk, Nacho woman, and especially Pootie.
“I’m going to dot your eyes becuase [sic] ya’ll lie so well. There’s something goin on you Gaumbies! Don’t get your panties in a wad. No way Baby! I didn’t do it, I wasn’t here. You Dogs are such Primas. Your Granny is a Fuzz Packet. DON’T YOU LOVE IT!
6-: From a letter to the Editor, by one John D. Tedder, published in The Daily Utah Chronicle (Salt Lake City, Utah, USA) of Friday 14th February 1986 [page 15, column 2]:
It’s an amusing notion to compare this whole Alta Club hullabaloo to racism. What, you think not letting women into the club is like not letting a minority eat in a restaurant? Give me a break.
[…]
Rather than getting your panties in a bunch over the exclusion of women by going to court, why not protest by creating a women’s club where men are prohibited. And then, ooohhh! Look at the tirade that will cause. Not a whimper.
7-: From FCC obscenity ruling makes 3 strikes, by Ken Hoffman, TV Editor, published in The Houston Post (Houston, Texas, USA) of Thursday 23rd April 1987 [page 8B, column 2]—the Federal Communications Commission (FCC) had ordered television and radio stations to clean up their acts:
Most of the morning jocks on the FCC’s blacklist will wear out their welcome soon enough. Why? Truth is, most of them aren’t very talented. […]
[…]
Howard Stern, the New York DJ who got the FCC’s panties in a bunch, is a different story. Stern is a genius at what he does. He’s outrageous. He’s angry, so full of himself and “over the line.” People love him and turn him on. People can’t stand him and tune in. Stern is a huge hit in a city where you have to go quite a distance to stand out.
8-: From an episode of For Better or For Worse, a comic strip by the Canadian cartoonist and author Lynn Johnston (born 1947), published in the Beauregard Daily News (DeRidder, Louisiana, USA) of Tuesday 30th August 1988 [page 9, column 5]:
MICHAEL, HURRY UP OR YOU’LL MISS YOUR BUS! DON’T FORGET YOUR LOCKER MONEY! TIE UP YOUR SHOES!!
LOOK, MOM, I KNOW WHAT I’M DOING, OK? …. DON’T GET YOUR PANTY HOSE IN A KNOT.
word histories 
I was curious when a friend told me of this item and then amused to see myself credited as an originator of “don’t get your panties in a wad” — which I assure you is not the case at all.
Although your search did turn up not one but two instances where I included the phrase in columns I wrote many years ago in my early 20s, I was pushing boundaries at the time and must simply have been the first employed writer for a legitimate newspaper irreverent enough to think that was a good idea — and to have editors who were indescribably decent people who weren’t suspicious enough to be looking for a smartass and didn’t think twice about any untoward meaning.
The columns you cite are from 1980, the year after I graduated college, and I assure “don’t get your panties in a wad” was around at least since 1974, when a buddy of mine used it often in high school. I also assure you it was intended as vulgar slang, a “wad” being common used as a synonym for a large amount of ejaculate. The version which now seems to be commonly accepted (a variation of knickers in a twist) makes perfect sense since both sound rather uncomfortable, but I submit this is an error in interpretation the original etymology.
Think about it: Who wears panties that are wadded or twisted? Whenever would that happen? And, ok, say it does and they ride up into your crack, isn’t it a simple enough matter simply to straighten them out in the ladies room and put them back on? On the other hand, if the panties you’ve removed in order to have sex end up covered with in semen, that’s a problem that might make someone much more short tempered.
I can’t vouch for my friend being the very first to say “don’t get your panties in a wad” (though it’s possible) — only that he used it often and gleefully, and it’s intended meaning was widely understood.
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