Green’s Dictionary of Slang

(Aus.) used in non-commercial senses, in addition to.

1905

Argyle Liberal (NSW) 7 Nov. 2/3: In the centre were a few eggs, and the damper and co. was very much in evidence, but beyond this there was nothing else to eat.

(orig. US) along with, together.

1869		J. Greenwood Seven Curses of London 91: Ask her what she knows about me, and she’ll tell you that, wuss luck, I’ve got in co. with some bad uns, and she wishes that I hadn’t.
1873		J. Greenwood In Strange Company 255: If one ain’t enough, let three or four of ’em go in Co. and do it.
1885		M. Davitt Leaves from a Prison Diary I 111: The ‘man of the world’ [...] is generally in Co. with a ‘lady hook,’ or a ‘pal’ of his own sex.
1914		E. Dyson Spats’ Fact’ry (1922) 40: Me and him’s been in co. for two months now.