People raising drinks in a cheers.
Glass-Clinking Etiquette Began As Medieval Poison Control

There is an aspect of toasting etiquette that always seems to say “Cheers,” regardless of language or culture: the touching or clinking of glasses.

This practice dates back at least to the Middle Ages, and its origins suggest a time much less trusting than our own when poisoning was quite common.

Clinking glasses could cause drops from a glass to go into another, show confidence in one's drinking companions, and ensure that any poison would be dispersed to everyone.

Medieval drinkers would pour a little wine into each other's glasses to ensure all were poison-free or touch glasses if they were confident in the absence of poison.

In his book "A History of the World in 6 Glasses," author Tom Standage posits that poison is implicitly absent in shared drinks, which were common in ancient Egypt and Mesopotamia.