Hi there!
Knackersknowle means "The hill of the knacker's yard".
If you open your Search Engine and then tap in Knackersknowle you will discover a vast amount of information - am sure you will be surprised!
Plymouth and West Devon Records Office at Clare Place, Coxside, Plymouth, telephone 01752 305940 has wonderful archives and they may be able to give you further information.
Another site you may like to look at is Plymouth Photographs.
Best wishes Priscilla