Given that in the US people are often quite creative when it comes to spelling, I went from Yencina to Jencina and finally to Jensina until finding something useful:
Jensina is indeed used in Scandinavian countries like Denmark, as a Google search e.g. for "Jensina Denmark" shows. It seems to be a female form of Jens:
http://www.behindthename.com/name/jens
Rene
www.BabyNames.ch