A mechanic I knew some years back liked to conclude his sentences with a verbal exclamation, “what I did.”
I would ask the status of one our mining machines and he would respond, “I just changed the oil in the D-9. What I did...”
I’ve always wondered where this came from.
The structure and conjugation are suggestive of Cajun/French English. I bet if you dug into his background you'd find either some Louisiana or Quebec connections and influence.