Just a guess here, but I seem to remember that name popping up in early medieval conmtexts like romances, gestes, etc.
I doubt that it is originally French, more likely a Latinized form of a Celtic name - I think this because of where I believe I've come across the name. I am an adult education teacher and I have a student whose firsty name is Ivelisse and she's alwsys been self-concsious of it becauxse no one she ever knew ever had that name, she always thought that her mother made it up.
The syllable "Lisse" is very common in German, names like Annelisse, etc. are still popular in Germany.
I'd appreciate some feedback, she's anxious and I'm curious, to get more data on the name
Thanks