bluff (v.) Look up bluff at Dictionary.com
1839, Amer.Eng., poker term, perhaps from Du. bluffen "to brag, boast," or verbluffen "to baffle, mislead." An identical word meant "blindfold, hoodwink" in 1674, 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."
bluff (n.) Look up bluff at Dictionary.com
1687, from Du. blaf "flat, broad," apparently a North Sea nautical term for ships with flat vertical bows, later extended to landscape features.