Smoke-Tan leather, also known as brain-tan leather, is perhaps best known today as the great skin-clothing tradition of indigenous North America. This is the oldest of leathers and the great gift that allowed humans to first live in temperate and cold climates. This is also the clothing of Palaeolithic Eurasia. The deer, many species of them, have been clothing northern peoples for something like 150 000 years. Being at the same time durable in the extreme, supple, soft, warm and breathable, this is the tannage that most preserves the qualities of actual skin in the finished material - there is nothing else like it. Try as they might, this type of leather cannot be produced industrially to anywhere near the same quality.
Smoke tan and brain tan get their names from the particulars of the way this leather is made. Put short, one employs both the animal's brains and smoke from particular plants or trees in the making. There are plenty of people online that will tell you more that they perhaps should about all this in very technical detail, and for that I refer you to them. I would rather say, perhaps more faithfully, and in keeping with an understanding of hide-tanning as a thoroughly mysterious and magical affair, that the skins must be fed. With great labor of preparation such that the skin might be able to eat again, followed by an elaborate protocol of feeding, specific fats become entwined in the molecular fabric of the skin such that they are once again returned to the supple and flexible way they were born to - as the place where the world and the animal meet, their covering, their house, their skin. With then again a second round of feasting, the skin is once more fed, this time with a hot meal of smoke. Again, when done right, our meal finds its way into the very structure of the skin, making permanent the blessings of the first meal, adding rich colour and water-resistance. This complex and learned alchemy is the sure sign of the keen observation of our and others' ancestors turning their astounding seeing powers and mytho-poetic sensitivities towards following and living with the animals, and a sure sign too of the benevolence of the world.