Green’s Dictionary of Slang

to defraud, to cheat, to betray, to abandon.

1856		Life in Boston & N.Y. (Boston, MA) 22 Nov. n.p.: I saw [...] the jewelry man amd H.J.T—g shising in an old second-hand boot shop.
1882		Dundee Courier (Scot.) 30 June 7/5: She swears she’ll be revenged on you for ‘shicing’ her and taking up with a darkey.
1902		H. Baumann Londinismen (2nd edn).