Fanny Adams?

A bit late with this, but I always understood 'sweet F A' or 'Fanny Adams' to be a euphemism for *beep* all'. A bit like 'mucking about' or 'flaming hell', or any number of other expressions in the same vein. I suppose it's about as close as they could get to an expletive in any film of the 40's. BTW, can you imagine a Cockney actually saying 'luv' a duck'? Dunkirk was about the first mainstream film to use 'soldier's language' and even that was mild by modern standards.
Being ex Royal Navy I know of another possible origin, here goes;

Miss Fanny (or Frances) Adams was a child aged 9 who was murdered at Alton, Hants on 24th April 1867. The murderer (Frederick Baker, a solicitor's clerk aged 24) cut up the body into pieces some of which were said to have been found in Deptford Victualling yard. Baker was tried at Winchester and hanged in December 1867. At about this time tinned mutton was introduced into the Navy and somewhat naturally it soon acquired the name of Fanny Adams. The tins themselves were found very useful by the sailors as mess gear (there was no official issue of mess gear in those days) and to this day the name FANNY remains attached to the small round "mess kettle" (similar in appearance to a painter's pot - also called a kettle).
I hope you find this interesting if not particularly useful.