Explaining an idiom: ‘knock on wood’

Idioms: Knock on wood?
Knock on wood is a superstitious idiom. It means something like “I really hope to avoid jinxing the outcome I consider desirable.”
Example:
  • Janet: How’s it going?
  • Bill: Things are really great! My business is doing super well, and I think we’re about to get a really big contract.
  • Bill: …knock on wood.

What Bill means is something “I think I’m going to get this contract, but I’m kind of worried that my confidence will jinx it. I am acknowledging this in hopes that it will protect me and that I will in fact get the important contract.”

“Take a rain check”

p-3a answered your question: Idioms?

“Take a rain check”?

“Take a rain check?” means:

  • In principle I would like to do the thing you are suggesting
  • For some practical reason, I can’t do the thing now
  • I want you to know that I do actually want to do the thing
  • Can we do it at some yet-to-be-determined point in the future?

I think it’s a reference to a practice some stores have with sales:

  • Sometimes they will advertise a sale
  • And then run out of the thing that’s on sale
  • And give people who want to buy it rain check, which is a piece of paper entitling them to buy the product at the sale price once it comes back in stock
  • Most stores don’t do this anymore, but some do