My mental picture of Q as a rather scholarly, kilted and bespectacled gentelman of Scotland was, thankfully, restored by the addition of his word apparently!
Q is correct (as always!) Many years ago I saw a movie called Hardcore in which two vice cops discussed the various street terms for sexual acts, and half-and-half was one of them. Oh, what my young virgin ears learned that night....
With the addition of an 'a', making it 'a half and a half', in Scotland that meant - probably still does - a large whisky and a half pint of beer as a chaser. Just shows one has to be careful what one says and where one says it!