Fritz

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late 19th century: abbreviation of the German given name Friedrich .

wiktionary

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Unknown. See on the fritz, which appeared in 1902. Possibly from German name Fritz, or onomatopoeia.

etymonline

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Fritz

German familiar form of masc. proper name Friedrich; as a characteristic name for a German attested by 1883; very common in World War I. Phrase on the fritz "inoperative, not working properly" (1903) is American English slang, of unknown connection to the name; the earliest references suggest a theatrical origin.