'décolleté' originates from French, specifically from the verb 'décolleter' (past participle 'décolleté'), where the prefix 'dé-' meant 'off/away' and 'collet' (from Latin 'collum') meant 'neck'.

'décolleté' entered English from French in the 18th–19th century as a noun/adjective referring to a low neckline; the French formation comes from Old French/Medieval uses of 'collet' (a diminutive of Latin 'collum' 'neck') plus the prefix 'dé-'.

Initially it referred to the exposed neck and upper chest area or a garment's low neckline; over time the word has retained this basic sense and is now commonly used to describe both the neckline and garments that reveal that area.