1913  Barn boss, the man in charge of the barn (or stables) in a lumber camp, on a large farm, in a livery, or wherever a large number of horses are kept.
1947  Barn Bosses . . . will work as many hours during the week as may be necessary to do the work in hand.
1964  One may see a visitor with a misty look in his eye; an old blacksmith, top loader, barn boss . . . or river hog who has returned to a fleeting glimpse of an era long gone by.