Someone who is undecided or wavering. The verb form is “to swither.” Comes from Scotland (topical!) and is in much more common use there. Almost onomatopoeic, or maybe just close to “slithering.”
More on this word from The Bottle Imp: http://bit.ly/1qYp9JZcan
Not necessarily on topic, but “The Bottle Imp” is a great name for a publication.
NoTrueScotsman 
I figured that if was anytime this word could make a comeback it would be right now. Some quick googling reveals 6 hits for switherer in the last week, 12 in the last month. That probably qualifies as a comeback.
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