(A). A huge pewter measuring-pot, containing at least three English quarts. Readers of Waverley will remember (in chap. xi.) the Baron Bradwardine's tappit-hen of claret from Bordeaux. To have a tappit-hen under the belt is to have swallowed three quarts of claret. A hen and chickens means large and small drinking mugs or pewter pots. A tappit was served from the tap. (See Jeroboam.)
Weel she loed a Hawick gill, And leugh to see a tappit-hen.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894