You're right, I'm forgetting names like
Hildegard, but that's 11th C., and even then this is a low German/Franconian form of the theme. If there is no -gert or -gerte, then these are more like Frankish names borrowed into
German use and not high
German formations. Prosaic use of the feminine word is difficult to assess outside of Gothic, as there is semantic cross contamination with masculine and feminine forms of the near homographic word for rod/goad.