bluffyoudaoicibaDictYouDict[bluff 词源字典]
bluff: English has two words bluff, one or perhaps both of them of Dutch origin. The older, ‘hearty’ [17], originally referred to ships, and meant ‘having a flat vertical bow’. This nautical association suggests a Dutch provenance, though no thoroughly convincing source has been found. The sense ‘flat, vertical, (and broad)’ came to be applied to land features, such as cliffs (hence the noun bluff ‘high steep bank’, which emerged in America in the 18th century).

The word’s metaphorical extension to people was at first derogatory – ‘rough, blunt’ – but the more favourable ‘hearty’ had developed by the early 19th century. Bluff ‘deceive’ [19] was originally a US poker term. It comes from Dutch bluffen ‘boast’, the descendant of Middle Dutch bluffen ‘swell up’.
[bluff etymology, bluff origin, 英语词源]
bluff (v.)youdaoicibaDictYouDict
1839, American English, poker term, perhaps from Dutch bluffen "to brag, boast," or verbluffen "to baffle, mislead." 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." Extended or figurative sense by 1854. Related: Bluffed; bluffing.
bluff (n.1)youdaoicibaDictYouDict
"broad, vertical cliff," 1680s, from bluff (adj.) "with a broad, flat front" (1620s), a sailors' word, probably from Dutch blaf "flat, broad." Apparently a North Sea nautical term for ships with flat vertical bows, later extended to landscape features.
bluff (n.2)youdaoicibaDictYouDict
1844 as an alternative name for poker; from bluff (v.). As "an act of bluffing" by 1864.