Discredit

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mid 16th century: from dis- (expressing reversal) + credit, on the pattern of Italian ( di)scredito (noun), ( di)screditare (verb), and French discrédit (noun), discréditer (verb).

wiktionary

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dis- +‎  credit. 

etymonline

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discredit (v.)

1550s, "disbelieve, give no credit to," from dis- "opposite of" + credit (v.). Meaning "show to be unworthy of belief" is from 1560s; that of "injure the reputation of, make less esteemed or honored" is from 1570s. As a noun, "want of credit or good repute," 1560s, from the verb. Related: Discredited; discrediting.