The term "Gull" (simpleton - fool) is dated from somewhere between 17th-19th century by the Dictionary of Historical Slang, but seems to have overlooked Thomas Dekker's 'Gulls Hornbook" (publisheshed sometime in the mid 1500s
An 1872 edition of the Hornbook is one of the prides of our book collection
The term was used by Shakespeare and is said to have medieval origins - possibly Celtic (Welsh or Cornish)
Jim Carroll