Flare up! flare up! is all the cry, in every square and street —
No other sound salutes your ear, whoe'er you chance to meet
Where'er you ride, or walk, or sit, or breakfast, dine, or sup,
They welcome you or quiz you with "Flare up, my boy! flare up!"
[Fraser's Magazine, April 1834]
1926, in reference to airplane crashes; 1936, "disintegration under stress, mental collapse" [Fitzgerald]; from the verbal phrase, from crack (v.) + up (adv.). The verbal phrase in the meaning "to break up laughing" is by 1967, transitive and intransitive. Its earliest sense was "to praise extravagantly" (as in not all it's cracked up to be).