Jill, what an excellent link for Kathy! I hadn't noticed it.
Kathy, Google is your friend.
Do try Googling with various search parameters.
My hard copy dictionary (heavy - 2v) gave - as did Web dictionaries - the ancient origin of sapper as one employed at working at saps, the building and repairing of fortifications (which, obviously, would include trenches). Though that seems to have been completely lost in the mists of time as far as the Sappers (formerly Sappers and Miners) of the RE are concerned. As is so often the case, the name has continued but the derivation is no longer relevant.
I did try Googling for RE and Aldershot in the nineteenth century but gave up - the RE seemed to have all sorts of branches including signalling, ballooning, etc, etc, etc - you name it!
Have you searched in the National Archives at:
http://www.nationalarchives.gov.uk/They have all sorts of records of army personnel.
Good luck,
Judy
