I used to be puzzled when my father said he was 'going to see a man about a dog'.

I was brought up to use the term 'lavatory', which, of course, means a place for washing.

As for 'ballocks' - I only guessed the meaning from the context, without which I pronounced it like 'ballast', 'ballet' and 'ballad', and I would have had no idea what you were talking about.