Word for the opposite of a target? [closed]

I have an event database that links two people - the person causing the event and the person the event targets. The latter column I call "target", but I can't think of a word to describe the person causing the event. So it could be a word meaning the opposite of target (which I cannot think of), or it could be something related like "instigator". However, I don't like "instigator" because it comes from a verb that is made a noun with the -or suffix. It's not that "instigator" and "target" are different parts of speech, but the word "style" is different. Is there a word for the opposite of (and in the same "style" as) target?

Solution 1:

I'd go with "event source" and "event destination" / "event target", or "event cause" and "event effect". Then there's "event trigger"; if we're talking about a database, it may even literally be a trigger.

But at the end of the day it's a matter of personal taste.

Solution 2:

Your system describes events which are caused by people and also which affect people. Such events have an effect on the person they target. This effect is effected by the person who caused the event. A person who affects someone by effecting an effect is an effector.

Sorry, I missed your "no -or" requirement until after I finished writing my answer. I'm still submitting it because it was fun to write.