I know the Social Security Administration maintains info on the popularity of names (all the way back to 1880, apparently!), but that doesn't tell me if the nickname I have in mind -- "Manda" for Amanda -- is a twentieth-century invention or not.
(Ultimately it isn't a big deal; this is a secondary-world fantasy, so I can technically do whatever I want, and the name is going into the story one way or another, due to outside factors. But the OCD part of my brain wants to know whether it suits a nineteenth-century-ish setting or not.)
As a side note, I looked through the archives for this tag, and was interested to see which cultures come up again and again in naming questions. Japanese is easy to explain -- o hai thar anime -- but what are community members doing that makes Russian such a frequent topic of inquiry? :-)
Update: Many thanks to everybody who responded. I appear to be safe with this particular name, but I'd love additional links to resources that track this kind of thing more generally.