Outbreak

wiktionary

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From Middle English outbreken, oute-breken, from Old English ūtābrecan(“to break out”), equivalent to out- +‎ break. Cognate with Saterland Frisian uutbreeke(“to break out; burst out”), West Frisian útbrekke(“to break out”), Dutch uitbreken(“to break out, burst out”), German ausbrechen(“to break out, erupt”).

etymonline

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outbreak (n.)

"eruption, a sudden and violent manifestation" (of disease, hostilities, etc.), c. 1600, from the verbal phrase; see out (adv.) + break (v.). Outbreak (v.) "to break out, escape confinement" (c. 1300) was still in poetic use in 19c.