chickenyoudaoicibaDictYouDict[chicken 词源字典]
chicken: [OE] Chicken is a widespread Germanic word (Dutch has kuiken, for instance, and Danish kylling), whose ancestor has been reconstructed as *kiukīnam. This was formed, with a diminutive suffix, on a base *keuk-, which some have claimed is a variant of a base which lies behind cock; if that is so, a chicken would amount etymologically to a ‘little cock’ (and historically the term has been applied to young fowl, although nowadays it tends to be the general word, regardless of age). Chick is a 14thcentury abbreviation.

The modern adjectival sense ‘scared’ is a 20th-century revival of a 17thand 18th-century noun sense ‘coward’, based no doubt on chicken-hearted.

=> cock[chicken etymology, chicken origin, 英语词源]
chicken (n.)youdaoicibaDictYouDict
Old English cicen (plural cicenu) "young fowl," which by early Middle English had came to mean "young chicken," then later any chicken, from Proto-Germanic *kiukinam (cognates: Middle Dutch kiekijen, Dutch kieken, Old Norse kjuklingr, Swedish kyckling, German Küken "chicken"), from root *keuk- (echoic of the bird's sound and possibly also the root of cock (n.1)) + diminutive suffixes.

Applied to the young of other bird species from early 13c. Adjective sense of "cowardly" is at least as old as 14c. (compare hen-herte "a chicken-hearted person," mid-15c.). As the name of a game of danger to test courage, it is first recorded 1953. Chicken feed "paltry sum of money" is by 1897, American English slang; literal use (it is made from the from lowest quality of grain) by 1834. Chicken lobster "young lobster," is from c. 1960s, American English, apparently from chicken in its sense of "young." Generic words for "chicken" in Indo-European tend to be extended uses of "hen" words, as hens are more numerous among domestic fowl, but occasionally they are from words for the young, as in English and in Latin pullus.
chicken (v.)youdaoicibaDictYouDict
"to back down or fail through cowardice," 1943, U.S. slang, from chicken (n.), almost always with out (adv.).