1. Lancashire dialect used to wish someone farewell.
Abbreviated from "See thee" i.e. "See you (later)".
2. Lancashire term used to draw attention to something (compare with the Welsh "Look you".
"Sithi, ah'm bound for t' be goowin' in a bit. So I'll sithi in t' pub toneet!"
From "I bet the Yanks struggle with this one" by A. Northerner.