What encloses a message for carrying. Also the shape of a sound's rise and fall over time.
Old French envelopper, en- (in) plus voloper (to wrap), a word of uncertain, perhaps Celtic, origin — the same voloper that gives develop its own unwrapping.
What encloses a message for carrying, or the shape of a sound's rise and fall over the time it is heard. Both senses hold something inside a boundary that gives it shape.