or old un, subs. phr. (common).1. The devil: see SKIPPER.GROSE (1785).
2. (common).A father.
1836. DICKENS, Pickwick Papers, xx. Its the OLD UN. OLD ONE, said Mr. Pickwick. What OLD ONE? My father, sir, replied Mr. Weller.
3. (racing).A horse more than three years old.
4. (theatrical).The pantaloon; the FOOLS FATHER (q.v.).