Old English cicen (plural cicenu) "young of the domestic hen, the young of any bird;" by early Middle English, "any chicken," regardless of age, from Proto-Germanic *kiukinam (source also of 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. By regular sound changes it should have become Modern English *chichen; the reason it didn't is unknown.
Generic words for "chicken" in Indo-European tend to be extended uses of "hen" words, as hens are more numerous than cocks among domestic fowl, but occasionally they are from words for the young, as in English and in Latin (pullus). Meaning "one who is cowardly or timorous" is from 1610s; adjectival 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) is by 1834. Chicken lobster "small lobster," is by 1947, American English, apparently from chicken in its sense of "young." To count (one's) chickens before they hatch "anticipate too confidently the obtaining or doing of something" is from 1570s. Chicken-fried steak (1937) is a U.S. Southern recipe that batters, breads, and fries a thin strip of steak in the way fried chicken typically is made.
"the young of the domestic hen," also of some other birds, mid-14c., probably originally a shortening of chicken (n.).
Extended 14c. to human offspring, "person of tender years" (often in alliterative pairing chick and child) and thence used as a term of endearment. As slang for "young woman" it is first recorded 1927 (in "Elmer Gantry"), supposedly from African-American vernacular. In British use in this sense by c. 1940; popularized by Beatniks late 1950s (chicken in this sense is by 1860). Sometimes c. 1600-1900 chicken was taken as a plural, chick as a singular (compare child/children) for the domestic fowl.
"the young of a chicken or domestic fowl," mid-15c. (early 14c. in surnames), a contraction of Middle English pulte, itself a contraction of polete "young chicken" (see pullet).
