envelope: [18] English borrowed envelope from French enveloppe in the sense ‘wrapper’, and more specifically ‘cover for a letter’, at the start of the 18th century. It was a derivative of the verb envelopper ‘wrap’, whose ancestor, envoloper, gave English envelop in the 14th century. As in the case of its first cousin develop, the origin of the verb remains a mystery.
It is a compound formed from the prefix en- ‘in’ and voloper ‘wrap’, but the source of voloper has never been satisfactorily explained. It may come from a hypothetical Celtic base *vol- ‘roll’, but an equally good candidate is late Latin *faluppa ‘husk’, from which come Italian viluppo ‘bundle’ and viluppare ‘wrap’. => develop
"a wrapper, an enclosing cover," specifically a prepared wrapper for a letter or other paper, 1705, from French enveloppe (13c.), a back-formation from envelopper "to envelop" (see envelop).
