tether
noun [ C ] uk/ˈteð.ər/ us/ˈteð.ɚ/
（尤指拴动物的）系绳;拴链
a rope or chain used to tie, especially an animal, to a post or other fixed place, usually so that it can move freely within a small area
Idiom
at the end of your tetheridiom C2 mainly UK (US usually at the end of your rope)筋疲力尽;一筹莫展
having no strength or patience left
By six o'clock after a busy day I'm at the end of my tether. 忙碌了一天后，到6点钟时我已筋疲力尽了。