[Buddha-l] ahosikamma etc

[Mitchell Ginsberg]

Hello all, 
Perhaps someone can help analyse a couple of terms here. 
Both of these can describe actions of an arahat, who do not create the seeds for any fruits of karma, so to speak. 
One is ahosikamma. I see this as composed of ahosi (aorist of hoti, as in Skt. bhavati) plus kamma. I can find it in the VsM although not in the Tipitaka. It would be action that was, as is is no longer operant. 
Is that verbal-nominal structure common in Pai? 
Second is a term I am not sure how to separate out/analyse. It is kammatthakata. I have not found that in the PTS Pali-English Dictionary, not in either the Monier-Williams nor the Edgerton dictionaries. 
I do not find karmartha, but do find arthakrta (made only with regard to utility, interested ... which I understand to be as in having a vested interest). 
Is there a negative particle in there somewhere? 
It would seem that as an equivalent of ahosikamma, kammatthakata would make more sense with a negative sense, rendering a meaning something like an action done without an interest, without a self-interested aim, as I might think would be the action of an arahat ... 
All clarifications and comments invited. 
Thank you. 
Mitchell