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1667, first used by Milton (probably on analogy of cherub/cherubim), back-formed singular from Old English seraphim (plural), from Late Latin seraphim, from Greek seraphim, from Hebrew seraphim (only in Isa. vi), plural of *saraph (which does not occur in the Bible), probably literally "the burning one," from saraph "it burned." Seraphs were traditionally regarded as burning or flaming angels, though the word seems to have some etymological sense of "flying," perhaps from confusion with the root of Arabic sharafa "be lofty." Some scholars identify it with a word found in other passages interpreted as "fiery flying serpent."
mentioned in Isa. 6:2, 3, 6, 7. This word means fiery ones, in allusion, as is supposed, to their burning love. They are represented as "standing" above the King as he sat upon his throne, ready at once to minister unto him. Their form appears to have been human, with the addition of wings. (See ANGELS.) This word, in the original, is used elsewhere only of the "fiery serpents" (Num. 21:6, 8; Deut. 8:15; comp. Isa. 14:29; 30:6) sent by God as his instruments to inflict on the people the righteous penalty of sin.