"No we can't - the authorship of many songs that have become 'folk' are known yet they have been taken up and re-identified with by communities and have become part of the culture of those communities.
Quite often, as in the case of the MacColl songs I mentioned, the original maker is not known by the people who have chosen to identify with it."
I agree, Shoals of herring, fiddlers green,caledonia,dirty oldtown, are all examples