E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Newgate Knocker (A).
A lock of hair twisted into a curl, usually worn by costermongers and other persons of similar stations in life. So called because it resembles a knocker, and the wearers of it are too often inmates of Newgate. Newgate as a prison is abolished, but many phrases referring to the prison still remain.