Does anyone know of a resource where I could find specifics on the historical frequency and popularity of particular nns? I realize this is tricky because nns aren't often officially recorded, but I'm interested in knowing about historical nn'ing trends.
For instance, when was Greta a popular nn for Margaret, and when was Maggie, Meg, or so forth the dominant nn? Or when did the use of Bill fall off or Liam take off?
Does such a source exist? Or can you think of other creative ways to find this sort of data?