Traditionally the administering of emetics, the trope worked in Sonnet 118, had three purposes: to renew the palate, to forestall the onset of sickness, and to counteract poison. The sonnet also picks up the motif of "palate", "cup", and "poison", left off at the end of Sonnet 114. The first pair of lines describes how "we our pallat urge"; "urge" means to 'intensify' or 'sharpen' the taste, but the word was used also of distillations which are 'urged' to a degree that a compound is yielded. "Appetites" are sharpened or made more acute ("more keen") with "eager compounds". A 'compound' is a medicinal concoction, in this case one that is sharp or "biting" like 'vin-egar', a wine that is made 'eager' or sharp. The second pair of lines explores emetics that are taken ("we purge") to "prevent" illnesses yet to come ("maladies unseen"). Emetics make us sick through vomit ("sicken"), so that we might avoid ailments ("shun sickness").