The animal chamois is a mountain goat. "Shammy leather" is unlikely to have anything to do with goat hides. Chamois leather is a specially prepared sheepskin.
It is possible to slice tanned skins into two, or even three, sheets of leather. Such thin pieces of hide are called splits. The inner split of a sheepskin, when tanned and treated with natural oils, and has the surface slightly roughened (a napped finish, or suede), becomes chamois leather.
The outer layers of any animal skin take the most wear, and so are thicker and stronger. The inner split is more porous, stretchy, and flexible.
The properties of chamois leather have mixed advantage. The softness and absorbency makes it an ideal material for use as a flannel or sponge. The oils do not affect the ability to hold water, and will add to the polishing effect. The washing will remove the impregenated oils, very quickly if soaps and detergents are used. Without the waxiness the leather becomes, as do all leathers, stiff and hard on drying.
I have bought cleaning "shammies" from the appropriate shelf in hardware departments. The most recent purchase, fro Lidle, had the leather securely stapled to cardboard backing sheet. The staples had not started to rust, yet, but left large holes through several layers of the leather. On unwrapping there was a scar across the surface. I used it for bookbinding by way of experience, but the product had to be for own-use only. Whilst good enough for use the cosmetic appearance would not support the reputation we wish to maintain.
My previous purchase was from an agricultural supplies store (Mole Valley Farmers) where three fairly unblemished skins were stapled loosely together and sold for a very reasonable price. If you wish to use chamois leather for craftwork then you take a risk buying wash-cloths.
Such purchases are a good alternative, for small amounts, to that of paying more for the better quality, thickness, and nap, that a leather merchant will supply. For most people minimum quantities and carriage costs mean that the high street is the better choice.
