not to be ron (or flip) about it, but I suggest 'nouniness', of which OED3 suggests "Also (Linguistics): the state or condition of being noun-like.", and cites as follows:

1978 Language 54 356 There are still further distinctions to be made among English nominal constructions with regard to their degree of ‘nouniness’.

so, Proper Nouniness

-ron o.