CLICK HERE FOR KEY TO SOURCES
earlier form of SMUGGLE (vb.)
From E-NED: smuckle corresponds to LG. smukkeln (G. dial. schmuckeln, schmucheln) or Du. smokkelen, while the slightly later smuggle agrees with LG. smuggeln (G. schmuggeln, Da. smugle, Norw. smugla, Sw. smuggla).
The origin of the term, and the precise relationship of the two types, is not clear.
From: Political Arithmetick,
By Sir William Petty, 1690
Chapter IV. That the People and Territories of the King of England,
are naturally near as considerable for Wealth and Strength, as those of France