Green’s Dictionary of Slang

darby n.2

[16C SE Father Darby’s bands, a moneylender’s bond of particular severity, which effectively bound the borrower to the lender while the debt remained outstanding]

1. [late 17C+] usu. in pl., shackles, fetters, handcuffs; thus darbies and joans, fetters linking a pair of prisoners; darby-ringer, a villain [for ety. for darbies and joans, see darby and joan n.].

2. [early 19C; 1980s+] in pl. in fig. use, anything that shackles one.

3. [mid-19C] in pl., sausages.

In compounds

darby-cove (n.) [cove n. (1)]

[mid-19C] (UK Und.) a blacksmith; thus darby crib, darby ken, a smithy.

darby roll (n.)

[early 19C] a style of walking that betrays an individual’s experience of fetters and thus time spent in prison.

darby’s fair (n.) (also darbies fair)

[mid-19C] the day on which a prisoner is moved from one prison to another, and must thus be fettered.