Smoking used to be a normal passtime in pubs. So every table had an ash tray on it, usually promotional ones from the brewery. Pub food for many of us was crisps. Crisp packets needed to be disposed of, but ash trays soon overflowed with crisp packets. So the art of folding crisp packets nice and small was born.
I know of two ways. The quicker and easier way leaves a kind of half-sphere shape. It’s not very neat, but it’s quick to do. The other way leaves one of these tiny triangles. It’s much neater, but does take a little more time and takes a bit more learning.
Now, there’s no smoking in pubs, so there are no ash trays. Not so much need for the skill, so kids these days don’t know how to fold up their crisp packets.