Trilogy minus one

The Man asked me today what you call two movies or books that go together. If there are three, it is a trilogy. So what do you call it when there's two?

I answered,

"Oh, two is a – "

And then my brain went completely blank. The Man waited for me to answer, and when I didn't he laughed at me.

"You're supposed to be an English teacher!" he said. "If there's a word for three movies there must be a word for two!"

"Pair!" I said, desperately. "Duo! Couple! Duet! Twin!"

That was a bit annoying, so when I got home I looked it up.

Two connected works of art = duology or dilogy
Three connected works of art = trilogy
Four connected works of art = tetralogy

And so on. (The list is here.)

Now I feel a little better about not knowing. Have you ever heard anybody call two connected movies a duology, or dilogy? Even if they did, you'd suspect them of making it up, wouldn't you?

I would, anyway.