'V-necked' originates from modern English, specifically the combination of the letter 'V' (the name of the letter 'V') and the noun 'neck' with the adjectival suffix '-ed' meaning 'having'. Here 'V' denotes a 'V-shaped' form.

'V-neck' developed from the phrase 'V-shaped neck' and became common in the 20th century as V-shaped necklines grew popular in clothing; the adjective 'V-necked' was formed by adding the suffix '-ed' to indicate 'having' that shape.

Initially it referred literally to a neck or neckline shaped like the letter 'V'; over time the meaning has remained essentially the same, used to describe garments with a V-shaped opening at the neck.