I know two girls named Jenica and one named
Jennica. The two Jenicas got their name because their parents weren't able to decide between
Jessica and
Jennifer.
Jennica got her name because her parents loved
Jennifer but thought it was too common. They all thought they made it up but it seems to be made up quite often. All were born in the 80s.
I doubt it has anything to do with
Joan. It's
Jessica +
Jennifer = Jenica.