You can use tail to refer to the end or back of something, especially something long and thin.
(尤指细长物体的) 尾部 The horse stood whisking its tail. 那匹马站着挥动尾巴.
To tail someone means to follow close behind them and watch where they go and what they do.
跟踪 He checked behind. No tail. 他看看身后——没有人跟着。