1670s, "juggler who appears to swallow fire as part of an act," from fire (n.) + eater. From 1804 as "person of irascible or recklessly defiant disposition;" especially in U.S. history in reference to vehement Southern partizans (1851). Perhaps due to the extended senses, fire-swallower began to be used for the original sense by 1883. Related: Fire-eating.
