DENIS is mentioned in Election Night Live 87, so was around a couple of years earlier than thought here (in some form at least) Jonathan 11:16, 9 July 2007 (BST)
I'm sure someone also said it stood for "Dynamic Election Night Information System" at some point during the 40th, when they were watching something over my shoulder. Richardash1981 12:43, 9 July 2007 (BST)
The name I listed came from comments in the 'REM' statements on the BBC Micro floppies, it's possible that that's the author's informal name for it and everyone else used 'EN' for 'Election Night'.