Hahaha "eshays" is derived from the word "session" actually, which is abbreviated to "sesh".
Eshays is Pig-Latin for sesh, and is *only* seriously used by "lads". They get together and have a "lad sesh", (congregate and stir sh*t) and one of them oh so cleverly attempted to manipulate the term by making it Pig-Latin = Eshays Adlay.
They're a really intelligent bunch.
Eventually, eshays became their tag and generally used it as a greeting or reply and an average person will use the term as mockery. I once actually said eshays to a group of lads on the train, and they threatened to "stab" me, along with a list of vulgar, derogatory terms. Mind, I was fifteen.
Lads aka scum of Sydney, are generally found around train stations and bus bays. My theory to this is because if the police show up, they can easily get away.
Lads are actually quite pathetic, and generally from a low socioeconomic class. Generally. They wear a striped polo shirt, Nike shoes, bum bags and a cap and are usually seen smoking, spitting or swearing. They're usually cowards, and threaten innocent people to fuel their own egos. They seldom actually hurt anyone, because they're so cowardly. But you get the occasional drugfucked lad, who *will* draw a knife.
Lads are a dying race, which is a good thing. But you've got to pull a weed out by it's root to kill it.