How old are you? Where did your parents find the name?
Most of the references to males name Nondas seem to indicate it is a Greek name as a male name.
The only reference I could find on short notice to Nondas as a possible Native American name is the following site which mentions a visit in 1791 to a town of the Seneca nation in what is now Livingston County, New York, called Nondas, with the claim that Nondas meant "high or steep hill". But with only one reference that has to be a "perhaps" derivation, not a sure one: