Green’s Dictionary of Slang

croaker n.5

[crocus (metallorum) n. (1)/croak v.2 (2), i.e. a pessimistic view of the profession]

1. [mid-19C+] (US) a doctor, esp. in drug use; thus croaker joint, a hospital or a surgery; nut croaker, a psychiatrist.

2. [1920s+] (US prison) the prison doctor.

In compounds

croaker’s chovey (n.) [chovey n.]

[19C] a pharmacy.