Definition of "drummer"

Bullock's liver will catch drummer.

1983, The Fisherman Who Laughed, page 67

Bennett's central figure, Ray, is first and foremost a serial "drummer" (housebreaker in crim-speak), and only secondly a human being, […]

1999, Theatre Record, volume 19, numbers 17-20

You know what life on the road is like — these poor salesmen when they don't sell some big account they been counting on why they go into one terrible slump they set there in the hotel room brooding over it and after a while they go out and meet some other drummer down in the lobby and start chewing the rag about all their troubles and then they get feeling so sorry they go across the street and commence drinking beer and about three hours later they come back to the room and write the house one of these here letters how rotten the product is.

1953, Richard Bissell, chapter 14, in 7½ Cents‎, Atlantic-Little, Brown, page 154