Smokie is the affectionate diminutive of Smoky: a color descriptor applied to grey or dark-coated animals for as long as people have been naming pets. The IE ending softens it, making it feel like a household nickname that hardened into a proper name through daily use. For a grey or dark-colored dog or cat, it's direct and satisfying.
The Coat-Color Naming Logic
Smokie sits in the grey-toned category alongside Ash and Shadow. The smoke association gives it more texture than a flat color word: smoke moves, shifts in light, has depth. That makes it more evocative than simply calling a grey dog "Grey."
Breed Fit
Smokie works especially well on Weimaraners, Greyhounds, and Scottish Terriers. On a Russian Blue cat it's almost too perfect. On a golden retriever it produces a dissonance that requires deliberate commitment to the irony.
The Counter-Reading: Tobacco Associations
Smokie inevitably carries cigarette and barbecue smoke connotations alongside the color meaning. Most owners find this irrelevant or funny. The name is common enough at low rank levels that it reads as sincere rather than ironic.