I remember the start of surprise I sustained when, many years ago, I heard a headmaster, not an Oxford man, refer to a pupil whom he had sent to ‘New’, and I can sympathise with Mr Seligman’s disquiet on hearing his college referred to in this way.
But why always ‘New COLLEGE’? Is it because ‘new’ is an adjective, as a friend of mine (from Corpus) suggested, or because ‘new’ is a monosyllable, or for some other reason? Perhaps only members of New College can tell.
There is an explanation of the Old English alliterative metre by C S Lewis. In it he gives examples in modern English of the metre and its variants. One of his examples is ‘New College knows’, so perhaps this is what New Collegians know.
To widen the enquiry; does anybody ever refer to Gonville and Caius College by its full name? A friend of mine who went there always spoke of ‘Caius’, sometimes pronouncing the word as Latin, by way of a kindness to an Oxford classicist.