I don't buy the "poison may slop into the others glasses" hypothesis as a) that's what loving cups (as drinking vessels which are passed around are now called) are for and b) it's not reliable (as a loving cup is) as a safeguard and c) since when did poorly paid warriors both i) want to lose beer and ii) not trust their comrades with whom they've been fighting. (Not to mention that olden fighters used swords and brute strength, it was the shamans, druids, wizards & so on who dealt in poisons - and a fighter didn't drink with them (except maybe by way of a loving cup). There's also a lack of evidence for that anyway. Also: it has to be remembered that drinking from glassware was confined to the rich until the last couple of hundred years. (Depend how you define rich, I guess) It's more likely to stem from 2 factors: 1) It's an inclusion thing - let's all get drunk together. But rather than the cumbersome hand shaking (and when did that start? now there's a question!) let's touch tankards. (Though there's scant evidence) (There''s a theory that touching glasses/mugs indicates trust. But you trust your host if you drink with them, otherwise you don't drink - Loving Cups are ceremonial - no single host. Also, you don't clink your tea-cups or coffee mugs together. ) 2) The "Ching" you get from a clinked pair of glasses shows that they are of good quality. A crystal glass chings much better than moulded glass. A good quality glass chings better than a poor quality one and, more importantly, will survive the clinking better. It all points to a mere showing off (based upon an established practice) , a kind of adult game of conkers, whereby a host can show-off the quality of their glasses. And the greatest of all show-offs of material possessions were the Victorians. And that's probably where it stemmed from. You are being sociable, you being inclusive, and you are showing off. Comments welcome. I'm off for another drink. Chink-chink.