Tansy,

You wouldn't really need to post pages of a thesis; you could say, for example, that feature x and feature y are similar to older forms of the words in question. Many of us here also have advanced degrees (I have degrees in Medieval Lit and in Folklore) and will not only understand but appreciate that kind of thing.

One caution, which of course you'll be aware of, is that older features survived into later written language; Chaucer writes the same words variously, sometimes in more archaic forms and sometimes in more modern forms. As you said, the only real proof would be an older manuscript, since we don't know when archaic forms of language definitively died out.