Old English mentel "a loose, sleeveless garment worn as an outer covering, falling in straight lines from the shoulders," from Latin mantellum "cloak" (source of Italian mantello, Old High German mantal, German Mantel, Old Norse mötull), perhaps from a Celtic source, or, if the Latin word is the same word as mantelum, mantelium "a cloth, hand-towel, napkin," perhaps it is from manus "hand."
Reinforced and altered 12c. by cognate Old French mantel "cloak, mantle; bedspread, cover" (Modern French manteau), also from the Latin source. Figurative sense "that which enshrouds, something that conceals, a covering" is from c. 1300. Allusive use for "symbol of literary authority or artistic pre-eminence" (by 1789) is from Elijah's mantle (II Kings ii.13). As a layer of the earth between the crust and core (though not originally distinguished from the core) it is attested from 1940. To take (originally have) the mantel (and the ring) was a symbolic act done before a bishop by a widow, indicating a vow of chastity (c. 1400).