two fields with the name "x"? perhaps you mean field "x1" and field "x2"?
Do you want the same value to also appear in "x2", once selected in "x1"?
Auto-enter can use another field.
x2 = x1
If there is ever a time to possibly have different data in the two fields, then two fields can be beneficial. If they will always be the same, why two fields?
1 field is fk used as popup to populate field, which is a #. I want the 2nd field to populate with a name that is within the same record by selecting the pop up choice. essentially I am looking for 2 different fields to populate once selecting the popup choice.
Define an auto-enter calculation for that second field that references the field from the related table.
Any reason you want to copy the name over, instead of simply displaying the related field on the layout?
btw, field x and y isn't really helpful. If you describe your real-world scenario, it's usually easier to provide advice.