A person with pyromania (an obsession with fire), or slang for someone who gets excited easily.
From Greek 'pyr' (fire). Used as a prefix in 'pyromaniac,' then shortened to 'pyro' in informal speech.
The term 'pyromania' was first used in psychiatry in the 1800s to describe people who couldn't control their urge to set fires—it's one of the oldest recognized psychological impulse-control disorders!
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