A 'snap' was indeed used by miners, and was a pressed tin box with a snap closure to keep the dust and muck out. 'Snap' is still used around the Black Country for a quick meal, or a snack.
'Viands' is from the French for 'meat', but used to describe any kind of food. 'Vittles' is from 'victuals', also a general term for grub of any description. Never heard 'cog-nogger' before, even though I spent years working in the Black Country. A thick sandwich was usually referred to as a doorstep. A 'piece' in our house was an inch-thick slice of bread spread with Stork, a real artery clogger.
When I was younger I had a rather posh girl-friend from Four Oaks whose family invited me for 'supper'. Now being an ordinary Brummie, 'supper' to me meant something scoffed last thing at night - in my case, for preference, dripping-toast with some Marmite. My posh bird's family used 'supper' as 'dinner' or evening meal - on that auspicious occasion I got a roast dinner, the beef burned to a cinder and the veg boiled to a soggy mess.
Big Gee