Green’s Dictionary of Slang

1. to get the better of, to beat.

1878		J.H. Beadle Western Wilds 41: More’n once the robbers would tackle some gritty man that was handy with his ‘barkers,’ an’ he’d get away with two or three of ’em.
1905		J.W. Carr ‘Words from Northwest Arkansas’ in DN III:i 81: get away with, v. To humiliate. ‘That got away with him.’.

2. (Aus.) to strike up a relationship with, to seduce.

1880

Bulletin (Sydney) 10 Apr. 3/4: ‘You girls call your sweethearts ‘darlings,’ and you men call yours ‘daises,’ [sic] and you girls are afraid to come up here for fear some other girls will get off with your ‘darlings,’ and you men for fear some other men will get away with your ‘daisies’ .