I have executed the following query (using COQL);

Select * From Accounts;

In this case I got NULL values for the AccountOwner_Name column. This is a Lookup datatype column. 

I modified the request to send "Owner_Name" since I thought this might be API's name for this column but I got an "Invalid column name" error. 

Could you please tell what is the correct API's name for this column ?

Note: I have tried sending only Owner but I got NULL values for this column.