I seem to remember someone telling me that -ko names were historically for Imperial family only, so maybe this list predates them coming into common use?
Nice to see historical Japanese names though - don't think we've had anything like this posted before. Quite a few of them are familiar to me as still in use, like
Hana &
Chiyo & Chise &
Yuki & Misa, but there are lots I've never seen before, e.g. Uta as a name. Do you know which ones aren't used any more?