Meaning

noun an angel of the first order; usually portrayed as the winged head of a child

originBack-formation of singular from plural seraphim, from Latin seraphim, from Biblical Hebrew שְׂרָפִים (sərāp̄īm), plural form of שָׂרָף (sārāp̄). The plural "seraphims" occurs in the King James Bible (Isaiah chapter 6). According to the Oxford English Dictionary, the singular "seraph" may have originated with John Milton, who used it in Book I of Paradise Lost (1667).

Etymology from Wiktionary, CC BY-SA 3.0