The meaning of "or two"?

An idiom or colloquialism for more or a lot.

I think it's pretty obvious, and I don't know that there's any "source". If it's good to have one friend when traveling, it's even better to have two. Peter bought something in the bookstore- we don't know exactly what, but we think it was a book or two. It's just an expression of estimating a number.

Uh, it's numbers. If you know a friend or two, then you know one or two friends. If you buy a book or two, then you buy one or two books. This is generally meant less literally. "It's good to know a friend or two when travelling overseas." usually means that knowing people where you are travelling to is a good thing because they can help you while you're over there and you won't be alone. Same with the book example. Peter bought a couple of books in the bookstore, is basically what they mean.

It means like its good to know at least one or two friends when traveling. And he just bought one or possibly two books

What sorry I dont know