Deviation

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late Middle English: via French from medieval Latin deviatio(n- ), from Latin deviare (see deviate).

wiktionary

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From Middle French deviation, from Medieval Latin deviatio Morphologically deviate +‎ -ion

etymonline

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deviation (n.)

late 14c., "a going astray, a turning aside from the (right) way or course, a going wrong, error," from Late Latin deviatus, past participle of deviare "turn aside, turn out of the way," from Latin phrase de via, from de "off, away" (see de-) + via "way" (see via). From 1630s as "departure from a certain standard or rule of conduct or original plan." Statistical sense is from 1858; standard deviation is from 1894. Related: Deviational.