Jolán

From various sources online, it seems that Jolanka is a diminutive of Jolan, not the other way around.

It's from Hungarian word jóleán meaning "good girl".

Hungarian etymologists will argue that this name is of Hungarian origin considering the fact that "jo lany" simply means "good girl" and that the name in its present form was created by a Hungarian writer and started to be used sometime in the 18th century. It may truly be just a strange coincidence that this name resembles the Spanish Yolanda, since given their geographies, these two countries had very little contact of any kind throughout the ages.