> The forms of the Latin gerund and gerundive .... I've searched a bit but
> haven't really been able
> to find anything on the matter,
Sihler (sections 567-8) has a good discussion of various aspects of the
possible development, and various possible origins, including the suggestion
made by Lars (squilluncus)
Gerhard Meiser, on the other hand, gives a different suggestion, not in
Sihler, and gives it as the only option: the -nd- element comes from the
same source as the -don- in cupido etc.
Peter