From the nursery rhyme. 'Popping' is a slang term for pawning, i.e. depositing articles with a pawnbroker in return for money. Weasel is a corruption of whistle - in cockney rhyming slang 'whistle and flute' i.e. suit. So, 'Up and down the City Road, in and out of The Eagle, that's the way the money goes, pop goes the weasel', describes spending all your money on drink in the pub and subsequently pawning your suit to raise some more.
Stewart Chaplin's story 'Stained glass political platform', 1900, contains 'Why, weasel words are words that suck the life out of the words next to them, just as a weasel sucks the egg and leaves the shell.' Theodore Roosevelt made use of the term in 1916 when criticizing President Wilson.
© 2004 The Phrase Finder
. Take a look at Phrase Finder’s sister site, the Phrases Thesaurus
, a subscription service for professional writers & language lovers.