In Reply to: Go to the bog posted by Alan Munn on July 09, 2008 at 21:44:
: I was told that to go to the bog (meaning to go to the toilet) referred to an era when toilets used to be down the bottom of the garden in a separate outhouse - hence ' going down to the Bottom Of the Garden. (British slang, possibly started during Second World War 1939-45-maybe even earlier)
'I was told...' - as unpromising a start as 'I have always thought that...'
'Even earlier' is right. Boggards, later called bogs or bog-houses, was the name given to privies from at least the mid 16th century.
The acronym source, as usual, is complete invention. Acronyms aren't found before the 20th century.