Food taster
A food taster is a person that takes food (or drink, in which case it's a cupbearer) to be served to someone else to confirm that it is safe to eat. The person to whom the food is going to be served is usually an important person (for example, a monarch) or anyone that could possibly be under threat of assassination or harm.
Food tasters have several functions:
The safety of the food may be determined by observing whether or not the food taster subsequently becomes ill. (Note, however, that food tasting would not be effective against slow-acting poisons that take a long time to show any visible symptoms.)
The food taster may also be responsible for the preparation and serving of food. The hope is that tasters will be diligent in preventing poison from being introduced into food, in order to safeguard their own lives.
In the event that the target (emperor, monarch, etc.) should fall ill or die, the similar illness or death of the taster provides evidence of deliberate poisoning.