a wooden dish; through Scottish (?) from French plaquette, plaque, a plate, whence English placard, Scottish placad. M`A. gives also the meaning "flat, broad, good-natured female", which is a metaphoric use.
a plack - a Scots coin; from Scottish plack, a copper coin equal to four pennies Scots, which came with the Flemish, etc., and is allied to French plaque, used of coin, though really a "metal dish, etc.". See placaid.