Green’s Dictionary of Slang

skelly n.1

[Scot. skelly, a squint, ult. OE sceolh, a squint]

(Irish) a glance, a look.

[Ire]L. Doyle Ballygullion 103: Sez Billy, takin’ a skelly at him wi’ the tail av his eye.
[Ire]L. Doyle Dear Ducks 191: He took a frightened skelly over at Hannah.
[Ire]Lynn Doyle Back to Ballygullion 59: He took a hasty skelly at his father.