god forbid/perish the thought

There are certain expressions we use to express how much we don't want a certain thing happening. It's like just mentioning the thought of something happening causes people a certain uncomfortable feeling and they need to turn to certain kinds of expressions to make it clear how much they hope something bad doesn't happen.

For example, your daughter is going to a party very late at night and you're very worried about her getting mugged or kidnapped or raped or anything bad that's constantly on the news. So you tell her: God forbid that someone causes you any harm out there on the streets. What I want you to focus here is the expression "God forbid", which as religious as it might sound doesn't necessarily imply a belief in God's direct intervention. It's become more of a way to merely express a strong wish. So it doesn't matter if you're a christian or even an atheist, some expressions that seem to have a very strong religious connotation don't necessarily reflect your beliefs and ideologies. Speaking of which, "God forbid" can also be "Heaven forbid", as in "Heaven forbid that they actually encounter a bear".

If you've never heard the expressions I've just taught you, you're very unlikely to know the following one: perish the thought. I don't have much to talk about that expression since its meaning is identical to both "God forbid" and Heaven forbid". If I could spot maybe a single peculiarity of that expression, I would say that this one expresses the idea of not even considering the thought of such a negative thing. It is used as a wish that what was just mentioned will never happen. So, take a look at this example: If you should become ill - perish the thought - I'd take care of you. That's all for today. Talk to you next time!