Amid fears that the end to more than five and a half years of talks would lead to a new era of tit-for-tat protectionism, negotiations between the United States and the European Union broke down.
Repayment in kind, as for an injury; retaliation. something bad that you do to someone because they have done something bad to you (Probably from tip for tap (1500-1600), from tip ( TIP) and tap )