I'll take Word and Gesture Origins for $1600, Alex

Found this on Fark:

The history of the birdie finger, and it's accompanying phrase. I've heard it before, but it's definitely worth reading again.

One time, we were in the meeting room. In an insurance meeting or something. And a co-worker (aged at the time 23 years and the assistant manager) and I (at the time 24, and the warehouse supervisor) made a game out of flipping each other the bird without the HR person (aged 45 or so) seeing.

After the meeting, I heard her asking the store manager in the exasperated belle voice that only southern women can achieve:

"What are they mad at each other about? They just kept flipping each other off the whole meeting!"

Yeah. We were clever.

A girl named Paula taught me how to flip the bird and what it meant in the first grade.

She also got in trouble for saying that there was an animal called the turd. And she also got in trouble for continuing to use the word turd in class after learning that it was indeed not an animal, and not a thing to be discussed in polite conversation.

I still bust out into peels of uncontrollable laughter whenever Chunk calls Mouth a turd in the movie Goonies, after Mouth slams the door in Chunk's face.

I can't think of anything else in my life relating directly to the word turd, but I'll be sure to write it here, if I do.