Fib

google

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mid 16th century: perhaps a shortening of obsolete fible-fable ‘nonsense’, reduplication of fable.

wiktionary

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Probably from fable; compare fibble-fable(“nonsense”).

Shortened from fibula.

fib (third-person singular simple present fibs, present participle fibbing, simple past and past participle fibbed)

Short for Fibonacci.

etymonline

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fib (n.)

"a lie," especially a little one, "a white lie," 1610s, of uncertain origin, perhaps from fibble-fable "nonsense" (1580s), a reduplication of fable (n.).

fib (v.)

"tell trifling lies," 1680s, from fib (n.). Seldom, if ever, transitive. Related: Fibbed; fibbing; fibbery.