The term 'tank-top' is a compound noun formed in the mid-20th century. Its first element, 'tank', is a shortening of 'tank suit', an early 20th-century term for a one-piece swimsuit worn in swimming pools, then colloquially called 'swimming tanks'. The garment evolved into a sleeveless top worn independently. The second element, 'top', derives from Old English 'topp', meaning summit or tuft of hair, which by the 15th century extended to mean an item of clothing for the upper body. The compound's logic is literal: it describes a top originally associated with, or styled like, a tank suit.

Structure: tank (sense) + top (sense) - tank: English (20th century). Functional role: Modifier, referring to a specific type of garment (a swimsuit). - top: Old English (topp). Functional role: Head noun, referring to an item of clothing worn on the upper body.