David,
I don't mean any offense, but I'll explain the American expression in case you have not heard it before. Pancakes are a liquid batter poured on a hot metal griddle that rise a little as they cook, but not very much. They are actually round and flat, and there is an expression we use that something is "flat as a pancake."
A pancake holster is two flat pieces of leather stitched around the contour of a pistol and around the edges that is flat as a pancake until we dampen the holster and insert the gun to mold it to the shape. It's still pretty flat, which makes the shape of the gun almost disappear under a jacket or shirt, so it is a very popular style of holster for concealed carry.
Hope this helps,
Mike