I asked yesterday about the word venatu. There was a good answer and good comments, but I want to ask a broader related question more specifically — especially due to TKR's comment. I want to know how the supine (e.g. venatum and venatu) is related to the derived fourth declension noun (e.g. venatus).
- Are the supine and the noun related historically? If so, how? If not, why so?1
- Is there a reason not to consider the supine just as two forms of the noun?2
- When did grammarians first make the distinction, if ever? That is, when where the supine and the noun considered as separate entities, assuming they weren't originally?3
The answer by fdb to this question about -us and -io implies that the supine and the passive perfect participle are unrelated (the similarity of their stems is coincidental), but there is no mention of the fourth declension noun. The question is related to this one, but the answers there do not seem to answer the question(s) asked here.
1 My guess is that some common uses of the noun developed into something that was later considered independent of the noun. But this is just a guess without any details.
2 I have no trouble reading difficile dictu (difficult to say) or te dictum misi (I sent you to speak) as if they had the noun dictus. I find the lack of preposition with the accusative a little odd in this reading, but only a little.
3 Any Roman remarks on the matter would be interesting. But if there are too many, I can split this into a separate question.