ORA-00955: name is already used by an existing object

The name of an object must be unique within a namespace. The ORA-00955: name is already used by an existing object error indicates that there is already another object in the same name namespace with the given name.

Ok (usually):

create table xyz;

After creating an object with the name XYZ, the following statements (as well as others) would throw ORA-00955: name is already used by an existing object:

create table xyz;
create view  xyz as select 1 one from dual;