“Bring that one by in a couple of days” What does “by” here mean?

Question

Conversation:

Librarian employee: I see you've got some books there. Is that the one you were asked to return?

Student: No, I left it in my dorm room. These are books I need to check out today. Is it OK if I bring that one by in couple of days?

Librarian employee: Actually, you need to return it today. That is if you want to check out those books today. That's our policy.

Student: Oh, I didn't know that.

What does "by" here mean?

There seems no idiom like "bring by," so I don't really know how to understand what this preposition "by" here means.

Answer 1

In your example, by has the same meaning as over here.

bring by
bring here
begin over

It's a shortened colloquial form for

over here
over to you
over there

Usually in reference to something which is stationary and often the location of a speaker

P1: I've got a new book!
P2: Bring it by when you get a chance so we can all have a look.

or

When I have some time, I'll stop by and say hello.
They stopped by on their way to the store.