Wormwood wine. Hamlet says to Laertes, Woul't drink up eisell —i.e. drink wormwood wine to show your love to the dead Ophelia? In the Troy Book of Ludgate we have the line “Of bitter eysell and of eager [sour] wine.” And in Shakespeare's sonnets;
I will drink Potions of eysell, gainst my strong infection No bitterness that I will bitter think, Nor double penance to correct correction.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894