Why did Fitzherbert say 'buyer beware' in Latin?

Fitzherbert likely rendered the phrase "buyer beware" into Latin to make it sound more official and legal-like. And it does. We still use "caveat emptor" in our modern financial laws. But the Romans who spoke Latin — and who had been dead about a thousand years — did not have a concept of this kind of relationship between buyer and seller.

Why do we say 'buyer beware'?

The risk is entirely on the buyer's shoulders. Fitzherbert likely rendered the phrase "buyer beware" into Latin to make it sound more official and legal-like. And it does. We still use "caveat emptor" in our modern financial laws.

Should a seller tell a buyer if he has a lame leg?

It's not up to the seller to tell the buyer if he has a lame leg or bad teeth; it's up to the buyer to use his eyes and hands to find these things out for himself. The risk is entirely on the buyer's shoulders. Fitzherbert likely rendered the phrase "buyer beware" into Latin to make it sound more official and legal-like. And it does.