1839, "to deceive (opponents), especially by betting heavily and with a confident air on a worthless hand to make them 'fold,'" an American English poker term, perhaps from Dutch bluffen "to brag, boast," or verbluffen "to baffle, mislead." The general sense "use a show of confident assurance to deceive an opponent as to one's real resources or strength" is by 1854. Related: Bluffed; bluffing.
An identical word meant "blindfold, hoodwink" in 1670s, but the sense evolution and connection are unclear; OED calls it "one of the numerous cant terms ... which arose between the Restoration and the reign of Queen Anne."
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<a href="https://www.etymonline.com/word/bluffing">Etymology of bluffing by etymonline</a>
Harper, D. (n.d.). Etymology of bluffing. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/bluffing