With apologies if it annoys, but I think this post from Jack Campin is informative

From: Jack Campin
Date: 09 Feb 20 - 06:41 AM

I just looked up mediation and related words in the OED. Seems the original mediator was Jesus Christ mediating between God and Man; later applied to the Pope's role; and it is first used in something like Harker's sense by Chaucer, describing his role as a scientific popularizer in his treatise on the astrolabe.


I remembered it when looking at the SOED. None of the definitions really fit.

I am left thinking that in the widest sense it is 'being between' or 'placing oneself between' two parties to convey some information or idea.

Jack quotes Harker "By mediation I mean not just simply the fact that people passed on songs … but that in the very process of so doing their own assumptions, attitudes, likes and dislikes may well have significantly determined what they looked for, accepted and rejected." but I think Harker's actual usage should go on", how they edited it and the way in which they selected from it, presented it or explained it."