backworm

plural backworms

1. obsoleteuncountableSynonym of filanders (“a disease of hawks”).

   Synonyms: filanders

2. countableobsoleteThe thread-like worm found in filanders.

   The Indian falcon is sick of the backworm

   August 1593, Walter Raleigh, letter

   2 more examples

   The backworm is rarely quite killed[…].

   1735, The Sportsmen's Dictionary, London: Printed for C. Hitch, at the Red Lion, and C. Davis, both in Pater-Noster-Row; and S. Austen, at the Angel and Bible in St. Paul's Church-Yard

   [... T]his, if any, may probably destroy that obstinate Disease of the Filander or Backworm.

   1964, Thomas Browne, “Of Hawks and Falconry, ancient and modern”, in Geoffrey Keynes, editor, The Works of Sir Thomas Browne, volume 3, London: Faber and Faber, page 62