The Swordfish received the 'Stringbag' nickname not because of its construction, but because of the seemingly endless variety of stores and equipment that the aircraft was cleared to carry. Crews likened the aircraft to a housewife's string shopping bag which was common at the time and, which due to its having no fixed shape, could adjust to hold any shape or number of packages. Like the shopping bag, the crews thought the Swordfish could carry anything.


By the time production ended on 18 August 1944, a total of 2,396 Swordfish had been built, the majority (1,699) by Blackburn, who took over the large scale production of the Swordfish from 1941 to allow Fairey to concentrate on its successors.


Fairey only did a part run of the Swordfish Mk I when Blackburn Aircraft in Sherburn took over. All subsequent marks (part Mk I, Mk II, Mk III and Mk IV) came from Blackburn and were normally refered to as 'Blackfish'.


Source:
Info: Wikipedia
Profile: Great Aircraft of the World
Published by Colour Library Books.