After 50 years of using "dogsbody" perhaps there was a need for a change of word: an event occurred which provided one.
In 1867 there was a gruesome murder in Hampshire UK of a young girl called Fanny Adams and the murderer's execution was the last public hanging in Winchester. Although canned meat had been bought by the Royal Navy from 1813 I think that the process was greatly improved around 1869. The contents, however, were not of good quality and in typical black humour the sailors then started to refer to them as "Sweet Fanny Adams" or "Sweet F.A." for short. In modern parlance, the latter now means something else: this side of the Atlantic at least.