According to this site:
http://www.ancestry.com/search/SurnamePage.aspx?html=b&ln=Disney&sourcecode=13304 Isigny is from the Romano-Gallic personal name Isinius (a Latinized form of Gaulish Isina). I have not been able to trace an etymology for Isina -- a wild guess could be the Goddess Isis, ad with Isidore.