Short answers, pulled from the story.
The word gang derives from the past participle of the Old English gangian, meaning to go or walk, and is cognate with the Old Norse ganga, meaning to go. This linguistic root suggests that the concept of a gang was originally neutral, simply describing a group of people moving together.
The first street gang in the country, the 40 Thieves, emerged in New York City around the late 1820s. This development occurred shortly after the American Revolution, which began in 1783, and was driven by the massive influx of rural populations into urban areas.
During the 17th century, London was terrorized by organized criminal groups known as the Mims, Hectors, Bugles, and Dead Boys. The Peaky Blinders became a famous street gang of the Victorian era that utilized unique slang to separate themselves from the rest of the population.
The hierarchy typically begins with the Boss, known variously as a leader, elder, don, or original gangster, who controls the movement, plans, and actions of the gang. Below the Boss is the Underboss, the second in command, followed by the Captain, who issues commands to the field and recruits new members.
Many street gangs, like the Bloods and MS-13, have a ritual where they beat up aspiring applicants for several seconds to show their toughness, willingness, and loyalty. The so-called morgue rule dictates that the only way to leave a gang is through death, subjecting defectors to severe retaliation.
The Bloods wear red bandanas, while the Crips wear blue, allowing these gangs to represent their affiliation. Any disrespect of a gang member's color by an unaffiliated individual is regarded as grounds for violent retaliation, and tattoos are also common identifiers such as an 18 above the eyebrow to identify a member of the 18th Street gang.