Why are odds of 33/1 known as ‘double carpet’?

In the heyday of the on-course betting ring, the job of the tic-tac was to convey information to his, or her, bookmaker, by means of a series of coded arm movements. Odds of 33/1 were conveyed by crossing the arms and placing the hands flat on the chest. Verbally, odds of 33/1 were and, in some cases, still are, called out as ‘double carpet’, which, like the arm movements, was intended to keep the information secret from anyone not ‘in the know’.

Betting ring vernacular often draws on sayings and slang including, but not limited to, backslang and Cockney rhyming slang, for its inspiration and ‘double carpet’ is no exception. In criminal, or prison, slang dating from the nineteenth century, the term ‘carpet stretch’ meant three months’ imprisonment; three months was reputedly the length of time required by an inmate to to weave a carpet or mat for his cell in the prison workshop. Thus, in the betting ring, odds of 3/1 became known as ‘carpet’ and, naturally enough, odds of 33/1 became known as ‘double carpet’.