Yardbirds

Part of speech: noun

Definitions

1. A term that refers to groups of informal musicians playing together in casual settings
2. A slang designation for young birds that have just left the nest, often used in informal contexts
3. A colloquial expression describing someone involved in low-level or minor criminal activities, typically in a less serious manner

Etymology: "Yardbirds" is the plural of "yardbird," a compound of "yard" and "bird." The "yard" is the open-air enclosure of a prison, where inmates were let out for exercise, and so a convict became a "yardbird," someone who spent his time in the yard. The term is attested in this sense from 1956. The same word had a second, unrelated life in the American armed forces during the Second World War, when it meant a basic trainee. Recruits drilling on the parade ground were treated much like prisoners exercising under guard, so the image of the barracks yard carried over from the prison to the training camp. The plural form "yardbirds" is what the sources record for the petty street criminal sense in the search results, and it is the form you asked about.