An idiom is a frequently used phrase within a culture that is interpreted to mean something other than what the words in the phrase literally mean. Idioms are colorful expressions, meaning rich, vivid expressions, that have developed because people feel the need to make language more vivid and varied. Since language varies in different cultures, idioms and their meanings will vary in different cultures as well. One example of a common English idiom is "taken aback," which has become a cliche expression to mean someone is surprised or confused (Cambridge Dictionary of American Idioms, 2003). It stems from the literal meaning of the word aback, meaning backward, which is no longer used in contemporary English.
Toni Cade Bambara's short story "Blues Ain't No Mockin' Bird" is full of dialect, and also contains a few idioms. The Woodland Hills School District of Pennsylvania points to one idiom: "with rocks all in his jaw." This idiom is very specific to the culture of the US Southern region in the story. The narrator explains that Granny frequently gets fed up with the—often racist—behavior of people around her, which is why the Cain family moves so much. The narrator further explains that each time Granny gets so angry she's ready to move again, Granddaddy first tries to pacify her, but by the next day he is "loadin up the truck, with rocks all in his jaw, madder than Granny in the first place." The idiomatic phrase "rocks in his jaw" doesn't literally mean the narrator's grandfather is sucking on rocks. Instead, it means his jawline is so tense from being angry that it looks like he has rocks in his jaw. In other words, it means he is very angry.
A second example of an idiom can be seen when Terry says, "I woulda gone upside her head with my fist and—." At this point in the narrative, Granny has just told the children her story of a person being disrespectful to a man who was suffering by taking photos of his attempt to jump off a bridge, and Cathy has added her own lesson of being disrespectful by telling the children her own version of "Goldilocks and the Three Bears." After Cathy explains that Goldilocks entered the bears' house uninvited, ate up the bears' groceries, and broke their furniture, Tyrone and Terry want to know what revenge the bears sought, and Terry uses an idiom to say he would have beat up Goldilocks. The idiom "upside the head" has come to refer to hitting someone on the side of the head. It was developed in America around the 1950s based on the actions of policemen: policemen used nightsticks to hit victims over the head, especially during civil rights protests (Ammer C., The American Heritage Dictionary of Idioms, 2003).