I am sorry - I forgot to explain that the form of 'habere' is in passive and
it literally means that '[a rock] is being held', which of course makes a
perfect sense, but the problem is that I have never come across such a
structure in such a context neither in Classical nor in continental medieval
Latin (it doesn't mean, of course, that it doesn not exist, but still I
would just like to exclude - or include - a possibility of the OI influence).