"one who lacks courage to meet danger or shrinks from the chance of being hurt," mid-13c., from Anglo-French couard, couart, Old French coart "coward" (no longer the usual word in French, which has now in this sense poltron, from Italian, and lâche), from coe"tail," from Latin coda, popular dialect variant of cauda "tail" + -ard, an agent noun suffix denoting one that carries on some action or possesses some quality, with derogatory connotation.
The word probably reflects an animal metaphoric sense still found in expressions like turning tail and tail between legs. Coart was the name of the hare in Old French versions of "Reynard the Fox." Italian codardo, Spanish cobarde (Old Spanish couarde) are from French. The spelling in English was influenced by cow (v. and n.).
流行于中世纪的法国民间讽刺故事诗《列那狐的故事》（Roman de Renart，英语译作Reynard the Fox）中有一只名叫coart的小野兔，它最大的特点是胆小。以后人们就常用coart来形容胆小的人。英语单词coward即是从该词逐渐演变过来的。其词尾-ard常作为贬义后缀，如bastard（私圭予），laggard（落后者），drunkard（酒鬼），sluggard（懒汉），dastard（卑怯的人）等。
但若究其根源，coart则又是源于古法语coue／coe（尾巴），拉丁语cauda（尾巴）。
把胆小鬼与尾巴相联系大概是因为胆小的人一受到惊吓总像狗一样掉转屁股就溜(turn tail)或是夹着尾巴逃跑(with tail between the legs)的缘故吧。