back of a beer mat

What does it mean when used figuratively?

What is the context? It is quite unusual as a figure of speech.

back of a beer mat economics/math, stuff like that

Are you talking about some bloke's sudden flash of inspiration and writing E = Mc² on the back of a beer mat?

I think so, but why would he do that? Why would someone want to write anything on the back of a beer mat? What does it mean if i literally write something on it?

a
Hi

When people drink in pubs and bars, they sometimes come up with unusual or crazy ideas that they feel they must write down straight away, so they can think about them the next morning. The nearest thing to hand is usually a beer mat. The metaphor can be used rudely or modestly:

- We're not going to bother with your design for the new engine part. Frankly, it looks lik

Hi again,

It occurs to me that the saying is a little difficult to understand because most beer mats, nowadays, are printed on both sides. The throwaway cardboard mat was introduced to the UK in the 1920s and, then, it would almost certainly have had a blank side

Here is the saying in action ...

wow, that is really an awesome explaination!

I wouldn't even know what it means literally! From the other comments, I'm guessing that a "beer mat" in the U.K. is what we would call a "coaster"" in the U.S. I think it would more common (in the U.S.) to refer to a sudden flash of inspiration being "scribbled on a napkin." (U.S. "napkin" = serviette, not diaper!!)

Hi

A similar expression that you hear in the UK but that is not in Merriam Webster is "back of an envelope calculation" (= an approximate calculation or sketchy plan, as if someone has hastily and very roughly done it on the back of an envelope)

Dave