Object#method returns a Method object giving meta-data about a given method. For example:
> [].method(:length).inspect
=> "#<Method: Array#length>"
> [].method(:max).inspect
=> "#<Method: Array(Enumerable)#max>"
In Ruby 1.8.7 and later, you can use Method#owner to determine the class or module that defined the method.
To get a list of all the methods with the name of the class or module where they are defined you could do something like the following:
obj.methods.collect {|m| "#{m} defined by #{obj.method(m).owner}"}