mantle

Where it comes from

Mantle came through Old English and Anglo-French forms from Latin mantellum, a cloak. It first named a loose outer garment, then anything that covers, surrounds, or envelops another thing.

How the meaning developed

That covering metaphor spread widely: snow forms a mantle, authority can be assumed like a ceremonial cloak, and geologists named the enormous layer between a planet's crust and core its mantle. Mantel, the fireplace shelf, shares the old word history but is now usually spelled separately.