The word "tankini" is a modern English portmanteau, a deliberate and playful blend of two existing fashion terms. It fuses "tank top," a style of casual upper garment, with "bikini," the iconic two-piece swimsuit introduced in the mid-20th century. The formation follows a common pattern in English where the first element ("tank") modifies the second ("-kini"), creating a new compound that precisely describes its hybrid nature: a swimsuit with a tank-style top and a bikini-style bottom. This lexical innovation reflects both marketing ingenuity and evolving trends in swimwear, offering a descriptor for a garment that provides more coverage than a traditional bikini while maintaining its two-piece form.

Structure: tank (top) + (bi)kini (swimsuit) - tank: English (from "tank top", a sleeveless shirt with a high neckline). Functional role: Specifies the style of the upper garment. - (bi)kini: English (from "bikini", a two-piece swimsuit). Functional role: Specifies the type of swimsuit, with the "bi-" prefix implied but omitted in the blend.