Grub Street is a derogatory term for bad writing. Its figurative use was commonplace by the early 18th cent. and Jonathan Swift referred to a paper he was involved with as ‘a little upon the Grub-Street’. In his Dictionary of 1755 Samuel Johnson commented: ‘originally the name of a street in Moorfields in London [now under the Barbican development], much inhabited by writers of small histories, dictionaries, and temporary poems; whence any mean production is called grubstreet.’

J. A. Downie

Grub Street used in reference to a world or class of impoverished journalists and writers, from the name of a street (later Milton Street) in Moorgate, London, inhabited by such authors in the 17th century.

Grub Street name of a street near Moorfields, London (now Milton Street), once inhabited by inferior and needy writers, transf. tribe of poor authors and literary hacks. XVII.