snollygoster has come up on these pages before (ycliu), but. today I received this from a "French lady in Tunbridge Wells, Kent/England":

Here's a word. It was in the Financial Times Polymath Crossword Puzzle Saturday (it's published lx/week). The word is SNOLLYGOSTER
Under that silly word hides a sad story. At the time of the Civil War, a mythical monster going under the above snollygoster name was invented to frighten the ex-slaves into not voting, in Maryland, of all places.

that didn't sound like the def'n that I remembered, so I liu again and found this:

I have snollygoster as "a shrewd unprincipled person", and OED2 gives "A shrewd, unprincipled person, esp. a politician."; but for etymology, OED adds: perhaps connected with snallygaster, which is, however, of more recent appearance.

snallygaster is then given as "[ad. G. schnelle geister, lit. ‘quick spirits’.] A mythical monster supposedly found in Maryland."

since both are given as U.S. dial., here is snallygaster from W3: Etymology: perhaps modification of Pennsylvania German schnelle geeschter, literally, quick spirits : a mythical nocturnal creature that is reported chiefly from rural Maryland, is reputed to be part reptile and part bird, and is said to prey on poultry and children.

likewise snollygoster: Etymology: probably alteration of snallygaster : an unprincipled but shrewd person.

but as pointed out by OED, snollygoster appears in print almost 100 years before snallygaster (1846 vs. 1940).

what then, given the French lady's def'n, is going on here? confusion? conflation?

quinion has a piece on snollygoster, complete with yet another spelling variant: http://www.worldwidewords.org/weirdwords/ww-sno1.htm