1. "I could give you a lift."

2. "These nylon ropes could give in to pressure."

In the above two sentences we use the simple past of "can" to refer to a future event.

I realize that this is perfectly grammatical. But what is this usage called ? Is it "unreal past" ?
simple past! they sound like simple present?
Debpriya DeBut what is this usage called ? Is it "unreal past" ?
could is one of the modal verbs. It's not called "unreal past". There's nothing unreal about it, and nothing past about it.

The first example shows how could can be like would be able to.

The second example shows how could can be like It is possible that ... will ....

I would be able to give you a lift.

It is possible that these nylon ropes will give in to pressure.

There is no name for it except to say that it's a modal usage.

CJ