As the essence of English idioms, the considerable amount, rich in content, widely application is an important part of English vocabulary. English idioms are often formed in the people’s mind. It is very polite and subtle. Therefore, people can not only keep in leaning idioms lively but also imitating application. It is also need to understand the deep structure of idioms. Especially in English learning in the language of the metaphor meaning. In order to cultivate and improve the creative use of English idioms ability. Idioms are an important part of the English language. It is also the essence in English. Each of an idiom seems to have their own specific forms. The historical origin, cultural connotation and the use of taboo. This requires the user to grasp it’s significance. Idioms are the cream of language with rich culture connotation in which colloquial metaphors often exist. With the development of cognitive linguistics, the study of idioms converts from the traditional figurative function to cognitive function. The conceptual metaphor presented by lake off is the important part of language should be used to explain the inner structure of the language. Through the analysis of related theories of cognitive linguistics, the cognitive mechanism of metaphor in English idioms is illustrated. It turns out that the cognitive analysis of metaphor in idioms not only accords with the law of language development but also helps to understand and apply the idioms correctly. Metaphor in English Idioms
1.2 The Origin of English Idioms
English idioms is the English national accumulated in the long –term social and historical practice taken place the special expression of a common ways. The source relates to people’s material and all aspects of life and spirit. Some idioms devived from the people’s daily life and customs. This idiom is in their own life and experience summing up. And it reflect the social tradition and customs.As it is indicated, If Jack is in love,he is no judge of Jill’s beauty.’’ “Jack’’ and ‘Jill’ is man’s and woman’s general meaning.but if literal translate into ‘Jack’ and ‘Jill’,people’s name.It may be misunderstand ,so, it should free translate into another proverb says “Love is blind’’. There are another examples: He lost the game and loses heart.Bill loses his heart to this beautiful girl. The two idioms use the ‘heart’ as metaphor. but their figurative is different. In the first sentence, lose heart’s meaning lose courage. but in the second sentence     ‘Lose heart’ meaning fall ;Love in this girl.
  There are idioms from Shakespeare drama and other literary works Pound of flesh, such as Savon drama. “The merchant of Venice’’(in the legitimate and unreasonable requirements).The Die is cast (Charlie Sans in what is done can’t be done)etc… From other literary works of idioms, such as Dickens “Bleak House’’ in the cry for the moon(Strive for the impossible);Defoe Robinson Crusoe in man Friday(Right-hand)etc.
All idioms, of course , show idiomaticity. However, all word combinations showing idiomaticity, for instance, habitual collocations such all these variations yield idiomatic expressions exemplifying idiomaticity, but they are not idioms. Idiomaticity is exemplified not only in idioms and conventional ad hoc collocations, but also in conventional  lexicog grammatical sequencing most apparent in longer text fragments :those smooth, plump. rosy cheeks will one day be shrunken, shriveled, and withered. This ad hoc sequence of adjectival modifiers preceding and following cheeks exemplifiers idiomaticity in both selection and sequencing, but  there are no combinations within the sequencing, but there are no combinations within the sequence qualifying as idioms, Such an ad hoc sequence can be compared with tall dark and handsome, an idiom both lexically and sequentially fixed. 英文论文英语习语中的隐喻研究(2):http://www.youerw.com/yingyu/lunwen_18264.html