We call it “the dance” or “playing hard to get” or something similar, and it’s an under-examined part of coupling discovery. A specific term for it would be nice so that we know just what we’re talking about, but I can’t think of one.
Perhaps we could think of it as surface tension, in the same way as water in a glass sticks slightly at the edges, the meniscus. It’s still water, but there is a definite boundary where the water meets air and the side of the glass.
In our case, part of the attraction of someone is the need to fight for them, or, if not exactly fight, then work at convincing them to conform to our vision of their affection. We want this person to be as attracted to us as we (think) we are to them. The oddity is that we don’t always want it to be immediate and complete; a little effort and time and salesmanship gives us a pride of ownership, that, like surface tension, keeps us glued together.
Think of it as the kind of camaraderie created by shared difficult experiences, such as in sport, business and war. Bonding is more piquant with adversity, which makes me think that a little difficulty in relationships might be the best way to make them stick.