What is the joke about the farmers daughter and the traveling salesman that everyone cuts off?
There are more than one. It’s a standard set up, not just one particular joke. It’s like “a guy walks into a bar…” There are a million jokes that start that way.
It goes like this:
Travelling salesman - why are seagulls called seagulls?
Farmer’s daughter - I don’t know, why?
Travelling salesman - because they fly over the sea! If they flew over the bay we would call them bagels.
There are lots of salesman/daughter jokes. Here’s one.
<make up your own setup here>
Farmer lets salesman sleep in the same room with daughter but puts chicken eggs on the floor between them to prevent visitation. Salesman has sex with farmer’s daughter, breaks all the eggs. He glues the eggs back together again to avoid detection.
Breakfast next morning, farmer breaks open a couple of eggs for breakfast, discovers they’re empty.
“Gertrude, the rooster’s been usin’ rubbers again!”
Oh, and it’s cut off because the joke always involves the salesman having sex with the daughter, or trying to.
Well, like Diogenes the Cynic, said there are many farmer’s daugther / travelling salesman jokes. Perhaps you were thinking of this one?
A farmer’s daughter enters the office of a vaudeville theatre manager and asks for a job in his evening variety show. The agent asks “What can you do?”
The farmer’s daughter brings in a variety of farm animals (horse, cow, sheep, goat) and (here’s where part of the joke is usually whispered in someone’s ear).
The talent’s agent jaw drops when he sees her act. “And what do you call that?” he asks.
“The travelling salesman”!
But I do believe that CookingWithGas has hit the nail on the head. That’s a much better GQ answer.
Rather than repeat the dirtier ones I know, here’s a small collection of them. “Farmers trap” is the one I most commonly heard growing up. We had a slightly different punchline involving the third guy grinning ear to ear and his tongue falling out.
The oldest known version of this joke is in the Satyricon of Petronius, Chapter 10 , where it involves a government official lodging with a family in the town he’s visiting.
This being Ancient Rome, of course, the landord’s offspring is a comely young boy. The gag is that, after several efforts to seduce the boy prove successful (all of which involve trying not to wake the father) the kid proves so insatiable that in the end it’s the official who threatens to wake the old man if the boy keeps pestering him for sex.
“The Aristocrats!”
Which one?
Ladies and gents, I present The Joke: The Musical from Mr. Show.
Great songs, Jack Black is in it, and don’t worry, it’s definitely not cut off. 
This is the quintessential salesman/farmer’s daughter joke as far as I’m concerned.
Just a word of warning - if you aren’t familiar with Mr. Show, this will probably be the funniest thing you’ve ever seen in your life.
I’m fairly it’s also related to “… and the Bartender says, ‘Hey, that’s not a spoon!’” or other half-punchlines/setups that imply a dirty joke… (as CookingWithGas already explained)
There’s no accounting for taste.
And Rachel Welch says “Those aren’t buoys!”
Rachel Welch, Raquel’s even bustier sister.
The traveling saleslady is rolling through the country on a very hot day, and her air conditioner is not working. She sees a pond, out in a very lonely field, and decides to have a dip. She parks her car, and walks out to the pond. Taking off her clothes carefully, she decides to leave them hanging on the fence, away from the mud and water of the pond.
She swims happily about, and then floats in the cool water for a bit. When she decides to get out, she finally notices the two farm boys sitting on the fence, by her clothes, grinning. She is very angry. She swims around the pond a bit, looking for something to help protect her modesty. At last she finds an old wash tub, half sunk and buried in the mud at the pond’s edge, opposite the boys. She pulls it into the water with her, and holding it up in front of her, she wades up out of the pond, and approaches the two boys.
“Do you know what I think?” she says to them angrily.
“Yep.” Says one of the boys.
“What?” she replies with some confusion.
“You think that there’s a bottom in that there tub.”
Tris
:smack: imanidiot