Head smashing was also present enough in episode 5x09 to give us reason to believe Negan is around. When Noah found his old house, he found his mother with her head smashed in the living room. Very similar to what Negan did to Glenn.
A trade-off is a situation where you make a compromise between two things, or where you exchange all or part of one thing for another. ...the trade-off between inflation and unemployment. American English: trade-off
Trade between two traders is called bilateral trade, while trade between more than two traders is called multilateral trade. Trade exists due to specialization and the division of labor - a predominant form of economic activity in which individuals and groups concentrate on a small aspect of production, but use their output in trades for other products and needs.