'A plague on both your houses!' Romeo and Juliet

[Oti]

Why was this such a bad insult at the time?

[RonBee]

Plague is a very bad thing. To wish the plague on somebody is to wish him ill. (The plague was a much more serious problem during Shakespeare's time than it is now.)

~R

[rewboss]

Also, of course, "house" here doesn't refer to a building; it's used to mean "family".

[Oti]

Thanks, both of you, for your help.