Green’s Dictionary of Slang

(Irish) the butt end of a cigarette.

1982		(con. 1930s–50s) E. Mac Thomáis Janey Mack, Me Shirt is Black 96: I’ll tell yer mother I saw you smoking dirty butts and stabbers.
1986		B. Geldof Is That It? 47: The stabber is reignited and the dash to the pub begins.
2001		G. Coughlan Everyday Eng. and Sl. 🌐 Stabber (n): the last 1/4 of a cigarette – ‘leave us a stabber’.