I have thought of Pallas Athene too... Here is the meaning of Pallas:

PALLAS f
Usage: Greek Mythology
Pronounced: PAL-as
Means "maiden" in Greek. In Greek mythology she was a friend of the goddess Athena, who accidentally killed her. Athena took the name Pallas in honour of her friend. (http://behindthename.com/nm/p.html#pallas)

I am not that sure that Pallis is derived from Pallas. Usually Greek people that have last names with two syllables (e.g. Pal-lis) come from a specific region of Greece (Ipirus, in Greek Ipiros). Maybe one of my grand-grand ancestors was born there...

George

P.S. I 'll ask my father about it, when he and my mother return from their vacations . Maybe he knows more...