I was born and raised in Gander and while I was exposed to a ton of Newfoundland wide sayings, Slue is one that was very much unique to Gander. I first recall hearing it from Glenn Powell who ran the Snack Shop across from the baseball fields. As Glenn would drive away on his motorbike he would let out a loud, long and very enthusiastic 'Slue!!!" and eventually I started hearing people my age using it. Fast forward many years and it is the last thing I say to my brothers when we part ways, often when the car is already driving down the road with no eye contact. I think at one point it might have been just a Newfoundlander responding to a French man who was using the French word for good bye, but no one knows for sure.
What is known is that if you are from Gander, you know this phrase and it is likely near and dear to your heart.