It’s paste.

The two words come from back when you literally copied a word again, cut it out with scissors and used paste (a thick type of glue) to attach it.

That’s some impressive google-fu you have there, Chris. I forgot that existed and have never gone to find how to do that.

You can answer your own question with a Google word frequency chart (Ngram chart).

Here is a frequency diagram of "copy and paste" and "copy and page."

Thanks so much for your answers, it is clear now.