I am 99.9999% confident there is no purpose for a vocative gerund. Yet nothing seems to specifically disallow for such a construction. In theory something such as "odi te currendum" (in English, "I hate you, running!") should be perfectly acceptable, albeit strange, ridiculous, and unnecessary. But is there ever a recorded instance of such a construction?
3I don't know the answer, but I would have thought that, if anything were used for such a scenario, it would be the infinitive, as it is for the nominative of the gerund and the accusative without a preposition.– cnreadJun 17, 2018 at 0:45
I've never seen the gerund used in the vocative, and a search for -ende in the Packhum corpus turned up nothing but imperatives. But I would be very surprised if such a form existed.
The gerund in general is defective, in that it has no nominative. If this missing form is needed, it's replaced by the infinitive.
Since the vocative is almost always identical to the nominative in Latin (the only exceptions being the masculine second declension, and a few scattered foreign words like Iēsus), I would expect the vocative of the gerund to also be identical to the nominative: that is, nonexistent, and replaced by the infinitive.
1Not really relevant to improve the answer, but besides Iesus, also the masculine 1st declension Greek names like Andreas– RafaelJun 17, 2018 at 18:03
"Cantandum est mihi": Even though Pinkster 2015 (pp. 301-302) analyses it as an impersonal gerundive (or a complex verb form with a passive deontic meaning), he does mention a number of researchers who argue that cantandum is a nominative gerund.– Alex B.Jun 18, 2018 at 2:17
@AlexB. Interesting! I'd never heard of that example, but I asked a new question about it ( latin.stackexchange.com/questions/6710/… ).– Draconis ♦Jun 18, 2018 at 2:23
@AlexB, mihi est construction is unique in itself. Bauer 2000 gives an interesting and convincing, although possibly controversial account of its being a relic of an earlier PIE. I read that example as “I have a certain piece not yet sung (but I must),” as an adjectival substantive deverbal, i. e. clearly a gerundive. I haven't read Pinkster, but a different understanding (“I have a singing”, “the singing is mine” like in est mihi pater?) seems to me like a stretch. Am I missing the point, what do you think? What are the arguments for the gerund here, and how can it be understood?– kkmJun 18, 2018 at 14:02