The English language has many expressions that describe a fast-moving event . Some expressions relate to body movements . We say something happens in the blink of an eye or in a heartbeat . Other expressions are related to the world of nature . Today we will talk about a speed-related expression involving an animal . But it is none of them . You guessed it ! The expression today involves sheep – baby lambs to be exact ! Lambs are cute . But they are not really known for their lightning speed . Well , our expression is about a specific part of the animal – its tail . I suspect lambs can shake their tails very fast . Because when something happens quickly , we say it happens in “two shakes of a lamb's tail .” Here is an example : “I'm going to the store . I'll be back in two shakes of a lamb's tail !” This expression is a cuter and more descriptive way of saying “quickly .” Maybe instead of sending a text message with the letters BRB (be right back ), we could use the image of a lamb shaking its tail . That would fun ! Being cute like a lamb may be fun . But it has its drawbacks . Cute things are often not taken seriously . And this cute factor is the main reason Americans rarely use “two shakes of a lamb's tail ” in a serious situation . For example , if I see a person get hit by a car , I would not say , “Hold on ! Help will be here in two shakes of a lamb's tail !” That would not make the injured person lying in the middle of the street feel reassured . In an emergency like that , I would say something like , “Help is on the way !” Generally speaking , an emergency is not a good time to use cute animal expressions . You should know that we often shorten this expression to simply “two shakes ” – as in , “I'll be there in two shakes !” You should not use that one for emergencies either . But we will be back in two shakes of a lamb's tail .