'double-convex' originates from Modern English as a compound of 'double' and 'convex'. 'double' comes from Old French 'double' (from Latin 'duplus'), where 'du-'/ 'duo' meant 'two'. 'convex' comes from Latin 'convexus', meaning 'arched' or 'vaulted'.

'double' passed into Middle English from Old French 'double' (ultimately from Latin 'duplus'). 'convex' entered English from Latin 'convexus' (via Late Latin/Old French influence) and became the modern English 'convex'. The compound 'double-convex' formed in Modern English to describe objects (notably lenses) that are convex on both faces.

Initially the components meant 'twofold' (double) and 'arched/convex' (convex). Over time the compound came to be used specifically in optics to describe a lens or surface that is convex on both sides.