Green’s Dictionary of Slang

the self, used with possessive pron., e.g. my jills, I; his jills, he.

1865		Leaves from Diary of Celebrated Burglar 106/2: I stood this a turn or two, until I felt convinced I was being ‘shoved;’ then [...] I left every one of ’em, and ‘grafted’ for my own ‘jills’. [Ibid.] 122/2: Others need only sufficient [violence] to ‘square their jills’ and secure a ‘get-away’ (safe retreat).
1886		Bulletin (Sydney) 31 July 17/4: In more than one instance, too, Joe ‘whipped the jills’ of his associates, but they ‘tumbled,’ and, being ‘fly,’ made some difficulties regarding the ‘mug’.
1906		E. Dyson Fact’ry ’Ands 101: ‘Go, sir, and prove it,’ falters me jills. ‘I can wait’. [Ibid.] 119: Fair dink, I wouldn’ be surprised iv ’is jills reaped off his tangled web iv whiskers.
1924		C.J. Dennis ‘Nocturne’ in Rose of Spadgers 51: I’m standin’ at the corner uv the Lane – / [...] waiting fer ’is jills.