I don’t think it is accurate to say that the ghettoes were made in part by the Jews themselves, unless you redefine the word to simply mean “neighborhood”.
The Jews were a cohesive community that was wary of assimilation into the larger community, and their communal institutions were located in the area where the Jews tended to live. Functionally, though, a ghetto was coercive and mandatory and was walled off from the rest of the city and closed off with gates that were opened only at prescribed times.
"redefine?" the etymogy says, " little borough" --if that isn't a "neighborhood," what is? It appears to be completely devoid of any unhappy connotations. So, it appears the redefining was done later, and accepted as the original.