Kaddish de'ischadita : A) origin? B) recited after a siyum?

Where did the first part of the kaddish which is said at a levayoh and at siyum originate?

Rallis

I believe that the saying of that kaddish by some at a siyum is a relatively recent development and that the older minhog is to only say it at a kevuroh, bar minan. Older editions of gemaras do not have that special kaddish in the back in the text for a siyum, rather just a regular kaddish dirabbonon.

The reason for saying it at a levaya is licheora poshut, since it mentions techiyas hameisim. But what shaychus does that additional segment inserted have with a siyum? Perhaps people often make siyumim in memory of niftorim, to coincide with occasions such as shloshim and yahrzeit, so some started saying it then too? However, minhag Ashkenaz is not to make festive siyumim on yahrzeit, as stated in MMA's Madrich leminhag Ashkenaz hamuvhak.

I suspect that it is not minhag Ashkenaz to say it at a siyum.

Litvak