Green’s Dictionary of Slang

bos-man n.

a farmer.

1859		Hotten Dict. of Modern Sl. etc. 10: Bosman a farmer: ‘faking a bosman on the main toby’ robbing a farmer on the highway.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 423/2: I’ve seen the swell bosmen (farmers) buy the pills to give to the people standing about.
1870		Hotten Sl. Dict.
1871–82		B.M. Carew Life and Adventures.