Whether during the drinks before a meal or at the end of a meal, it’s pretty common for guests at a dinner party to toast while wishing each other good health.
This practice dates back to the Middle Ages. During this epoch, it wasn’t too rare to die from being poisoned or from inadvertently ingesting some poison during a meal. To cut down on the risk, it was custom to touch your drinking glass against those of your fellow guests before drinking in order to pass a bit of the liquid from person to person. If the charming party-goer to whom you proposed to clink your respective glasses refused your offer, you could then be justified in having serious doubts about the contents of your drink. On the other hand, if they accept your humble invitation, then they will in turn gentlly hit their glass against yours. In this way, the respective guests could ascertain the loyalty of their fellow guests (or perhaps just the lack of homicidal tendencies) as well as generally feel more merry and at ease during the celebration knowing that their mortality won’t be tested during the course of the evening.
The expression ‘To health!’ associated with this gesture also comes from the same practice; if there is no poison in the glass, one consequently ‘wishes’ oneself good health by virtue of not incurring bad health. Today, however, toasting is usually more of a symbol of friendship rather than a skeptical search for sly murderers and deadly chemicals.