hmmm. So you have a charter. Actually, you have lots of charters. And the editor of the charters has given them titles according to the names of the people who make the donation (or whatever). This makes sense... except that a lot of the donations appear to be made by trustees, who are merely passing along someone else's donation, as it were. So legally, they are the donors. Functionally, though, they sort of aren't, in the sense that monastic donations are normally made in the hopes that someone's sins will be remediated (although I came across one today that actually uses pro absolutione peccatorum). The trustee is just a middle man whose job is to fulfill someone else's wishes (or to grant permission, depending on the sort of trustee it is).
Add to that the fact that there are two different sorts of trusteeship, as far as I can tell (and is manu potestativa really a livery of seisin in the C9th and C10th?) and it makes for interesting reading. Except that I can't recall having read anything in particular that splits out donors of origin from donors who are trustees (and especially donors who are trustees whose relationships to the donors of origin are unclear, except when noted or when they are counts or other officials).
I have actually read my way through Bresslau, and Beumann, and Ewig, and any number of other godsawful German paperweights designed to tell us about such things, and I don't remember seeing much discussion of this -- but then there is a soporific quality to such reading...
So, hivemind, can you think offhand of anything that clearly articulates what we mean by 'donor' and if it takes into account donations made by trustees? More specifically, can you think of anything that talks about such things pre-11th (or even 10th) century and Frankish?