as it was originally here in Grimsby comes from the term ‘white-death’ when you smoke too much weed, get paranoid, feel really dizzy and sometimes puke everywhere. It was known as ‘white-deathing’ then got shortened to ‘deathin’ and was applied to any unpleasant situation based feelings... well it was when i was growing up anyway...
I'm off home, i'm fucking Deathing mate!
look at that fanny, he's only had one bucket and he's Deathing!
You're a right Deather!