You can't rip apart that word into "auf" and "passen" and then individually translate them literally. The result seems nonsensical. I would say "aufpassen" is literally "be attentive" / "be watchful".
Edit: "to pay attention" is literally "Aufmerksamkeit zollen"
> You can't rip apart that word into "auf" and "passen" and then individually translate them literally.
Sure, just like you can't separate "pay attention". Both are idiomatic. But you can separate "aufpassen" into "Paß auf". (For the benefit of non-German lurkers, "Paß auf" is a command to pay attention.)
Edit: "to pay attention" is literally "Aufmerksamkeit zollen"