Perhaps surprisingly, the Goodyear Welt—a must-have for connoisseurs of serious wingtips—has nothing to do with car tires.* As you may or may not know, a welt is a strip of material (often leather) sewn around the bottom edge of a shoe; it joins the upper to the insole, and folds out to form a point of attachment for the outer sole. (Look at a pair of Doc Martens—the welt is the flat, stitched skirt of sole extending beyond the upper.) Once the outer sole has been attached to the inner (it’s often glued, with a layer of porous material such as cork in the middle to aid breathability), the different layers of the sole are sewn together, through the welt, with one thick stitch. This is the hallmark of the so-called “Goodyear welt.” Crucially, this stitch runs around the outside of the sole, rather than piercing the part under the foot, which makes the sole fully waterproof.
In contrast, Blake construction (the other main method for dress shoes) involves folding the shoe’s upper underneath itself and stitching it directly to the sole with threads that puncture the face of the sole; these stitches can allow for the transfer of water to the inside of the shoe. The disadvantage of a welt is that it adds bulk to the shoe, as its outer edges need to be wide enough to accommodate stitches. Between the Italians and the British, you can probably guess who, historically, has chosen slim soles, and who has been more concerned with dry feet.
* Charles Goodyear invented Vulcanized rubber—which made Brazilian tree sap stable enough for industrial use—in 1841. Although he was arguably denied proper recognition during his lifetime, his invention was important enough for the founders of Goodyear tires to name their firm in honor of him four decades later. Goodyear’s son, Charles, Jr., inherited his father’s inventiveness, and in 1871 patented the Goodyear Welt sewing machine, which attached shoe soles in a way that improved breathability, strength, and water resistance.