Dear tsuwm: can you tell us which one of these opinions is correct?
He did. The thread can be read at:
http://wordsmith.org/board/showthreaded.pl?Cat=&Board=words&Number=1717. Q&A, thread title Often, posted June 2, 00.

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tsuwm
(enthusiast)
Wed Jun 14 23:29:57 2000
Re: posh

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elegant, fashionable, fancy (slangy)

there is an interesting story behind the origin of posh-- http://quinion.com/words/qa/qa-pos1.htm
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Well-I could not get this link to work,
but this one should:
http://www.quinion.com/words/qa/qa-pos1.htm
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Re: sailors called taffs--this is reminding me of my
barrow-boy guess, but could it be because of the association with salt-water taffy?